GED Math : Finding Slope and Intercepts

Study concepts, example questions & explanations for GED Math

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Example Questions

Example Question #41 : Finding Slope And Intercepts

Two points on a line are \displaystyle (1,3) and \displaystyle (3,7). Find the slope of the line. 

Possible Answers:

\displaystyle -2

\displaystyle 1/2

\displaystyle 2

\displaystyle -1/2

\displaystyle 1

Correct answer:

\displaystyle 2

Explanation:

In order to find the slope of a line when given two points, you must use the equation

\displaystyle m = (y_{2} - y_{1})/(x_{2}-x_{1}), with \displaystyle m standing for slope. 

In the equation \displaystyle y_{2} is the \displaystyle y coordinate of the second point, \displaystyle y_{1} is the \displaystyle y coordinate of the first point, \displaystyle x_{2} is the \displaystyle x coordinate of the second point, and \displaystyle x_{1} is the \displaystyle x coordinate of the first point. Therefore,

\displaystyle y_{2} = 7\displaystyle y_{1} = 3\displaystyle x_{2} = 3, and \displaystyle x_{1} = 1.

Once you plug in all the numbers into the equation for slope, you get

\displaystyle (7-3)/(4-2)

which simplifies to 

\displaystyle 4/2, or \displaystyle 2.

Therefore, the slope is \displaystyle 2.

Example Question #42 : Finding Slope And Intercepts

Find the slope of a straight line that passes through \displaystyle \small (-2,-5) and \displaystyle \small (3,5)

Possible Answers:

\displaystyle \small m=2

\displaystyle \small m=-2

\displaystyle \small m=\frac{5}{2}

\displaystyle \small m=-\frac{5}{3}

\displaystyle \small m=\frac{5}{3}

Correct answer:

\displaystyle \small m=2

Explanation:

In order to find our slope, we'll need to use the slope formula, which is \displaystyle \small m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}

To find out what number goes where, know that whatever coordinate comes first is coordinate \displaystyle \small 1 and the one following that is coordinate \displaystyle \small 2. Also know that \displaystyle \small x comes before \displaystyle \small y in a coordinate.

In math terms, our coordinates should look like this: \displaystyle \small (x_{1},y_{1}) (x_{2},y_{2})

Following this guide, we know that \displaystyle \small y_2 must be \displaystyle \small 5, \displaystyle \small x_2 must be \displaystyle \small 3, \displaystyle \small y_1 must be \displaystyle \small -5and \displaystyle \small x_1 must be \displaystyle \small -2.

Now that we know what goes where, place the numbers into the formula and solve for m:

\displaystyle \small m=\frac{5--5}{3--2}

Subtracting a negative is the same as saying adding a positive number. If this confuses you, then try this rule of thumb:

Leave, change, opposite. 

This is how you determine if the equation will add or subtract if you have wonky equations such as subtracting a negative. You leave the symbol of the first number alone and you change the second symbol as well as the third.

Let's look at \displaystyle \small 5--5 for this.

\displaystyle \small 5--5 can be rewritten as \displaystyle \small +5- -5. We leave the positive \displaystyle \small 5 alone, change the subtraction to adding, and then make opposite of the negative \displaystyle \small 5, which would be positive \displaystyle \small 5.

This changes our equation to \displaystyle \small +5 + +5, which can be rewritten to \displaystyle \small 5+5.

Now that we know how to subtract a negative, our equation should be \displaystyle \small m=\frac{10}{5}, which can be simplified to \displaystyle \small 2 since \displaystyle \small 5 goes into \displaystyle \small 10 twice.

Our answer is \displaystyle \small m=2

Example Question #43 : Finding Slope And Intercepts

Find the slope for a straight line that passes through \displaystyle \small (2,4) and \displaystyle \small (8,10)

Possible Answers:

\displaystyle \small m=-1

\displaystyle \small m=1

\displaystyle \small m=2

\displaystyle \small m=-\frac{2}{3}

\displaystyle \small m=\frac{2}{3}

Correct answer:

\displaystyle \small m=1

Explanation:

In order to reach the answer, we must first employ the slop formula; \displaystyle \small m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}

To figure out what number goes where, know that whatever coordinate is given first in the answer is our coordinate \displaystyle \small 1, and the one following that is our coordinate \displaystyle \small 2. Also remember that \displaystyle \small x comes before \displaystyle \small y in a coordinate.

In math terms our coordinates should be \displaystyle \small (x_{1},y_{1}) (x_{2},y_{2}). Following this example, our \displaystyle \small y_2 must be \displaystyle \small 10, our \displaystyle \small x_2 must be \displaystyle \small 8, our \displaystyle \small y_1 must be \displaystyle \small 4 and our \displaystyle \small x_1 must be \displaystyle \small 2.

Now that we know what goes where, plug in the numbers to our slope formula and solve for m:

\displaystyle \small m=\frac{10-4}{8-2}

\displaystyle \small m=\frac{6}{6}

Because \displaystyle \small \frac{6}{6} is the same number, we get \displaystyle \small 1

Our answer is \displaystyle \small m=1

Example Question #41 : Finding Slope And Intercepts

Find the slope of a straight line that passes through \displaystyle \small (1,2) and \displaystyle \small (5,8).

Possible Answers:

\displaystyle \small m=-\frac{2}{3}

\displaystyle \small m=\frac{3}{2}

\displaystyle \small m=-\frac{3}{2}

\displaystyle \small m=\frac{8}{5}

\displaystyle \small m=\frac{2}{1}

Correct answer:

\displaystyle \small m=\frac{3}{2}

Explanation:

In order to find the slope, you'll need to use the slop formula, which is \displaystyle \small m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}.

Our \displaystyle \small y_2 is \displaystyle \small 8, our \displaystyle \small y_1 is \displaystyle \small 2, our \displaystyle \small x_2 is \displaystyle \small 5 and our \displaystyle \small x_1 is \displaystyle \small 1.

If you're confused on why I labeled our numbers like this, know that whatever coordinate your given first is your coordinate \displaystyle \small 1 and your next coordinate is coordinate \displaystyle \small 2

In math terms, our coordinates look like this \displaystyle \small (x_{1},y_{1}) (x_{2},y_{2}).

Now that we know what number goes where, it's just a matter of solving the equation for \displaystyle \small m.

\displaystyle \small m=\frac{8-2}{5-1}

\displaystyle \small m=\frac{6}{4}

Now we could leave our answer like that, but our fraction can actually be reduced even further. See how both the \displaystyle \small 6 and the \displaystyle \small 4 are divisible by \displaystyle \small 2? Because they share this \displaystyle \small 2, we can divide both the \displaystyle \small 6 and \displaystyle \small 4 in order to get the smallest fraction without changing what the fraction stands for.

\displaystyle \small \frac{\frac{6}{2}}{\frac{4}{2}}=\frac{3}{2}

If you're confused on why we can do this, pick up a calculator and find out what the decimal equivalent of \displaystyle \small \frac{6}{4} is, then with \displaystyle \small \frac{3}{2}.

Did you get the same answer? That's because \displaystyle \small \frac{6}{4} and \displaystyle \small \frac{3}{2} are the same answer, but \displaystyle \small \frac{3}{2} is just a smaller version of \displaystyle \small \frac{6}{4}. It's the same for if we multiplied \displaystyle \small \frac{6}{4}with \displaystyle \small 2, \displaystyle \small 3, or \displaystyle \small 4. Give it a try when you have the chance!

Our final answer should be \displaystyle \small m=\frac{3}{2}

Example Question #42 : Finding Slope And Intercepts

The point \displaystyle (1,2) appears on a line with slope \displaystyle 3. What is the \displaystyle y intercept of the line?

Possible Answers:

\displaystyle 0

\displaystyle 1

\displaystyle 2

\displaystyle -2

\displaystyle -1

Correct answer:

\displaystyle -1

Explanation:

For this problem you are given two values, the coordinates of a point, and the slope. The missing value is the \displaystyle y intercept. You therefore need to plug in what you know to the slope-intercept equation - \displaystyle y = mx + b - and solve for what you don't know. \displaystyle y is the \displaystyle y coordinate of your point, \displaystyle m is the slope, \displaystyle x is the \displaystyle x coordinate of your point, and \displaystyle b is the \displaystyle y intercept. So, you know \displaystyle y\displaystyle m, and \displaystyle x and you need to solve for \displaystyle b.

Once you plug in \displaystyle 2 for \displaystyle y\displaystyle 3 for \displaystyle m, and \displaystyle 1 for \displaystyle x, you get \displaystyle 2 = 3(1) + b, which simplifies to \displaystyle 2 = 3 + b. After you subtract the \displaystyle 3 from both sides of the equation, you find out that \displaystyle b = -1. Therefore, your \displaystyle y intercept is \displaystyle -1.

Example Question #41 : Finding Slope And Intercepts

Find the y-intercept of the following linear equation:

\displaystyle 4y-48=16x

Possible Answers:

\displaystyle (6,4)

\displaystyle (12,0)

\displaystyle (4,4)

\displaystyle (0,12)

Correct answer:

\displaystyle (0,12)

Explanation:

Find the y-intercept of the following linear equation:

\displaystyle 4y-48=16x

The y intercept is where a line crosses the y-axis. At this point, our x value must be 0.

To find our y intercept, we simply need to plug in 0 for x and solve for y.

\displaystyle 4y-48=16(0)

\displaystyle 4y-48=0

\displaystyle 4y=48

\displaystyle y=12

So, our answer is:

\displaystyle (0,12)

Example Question #111 : Linear Algebra

Find the slope of the following linear equation:

\displaystyle 4y-48=16x

Possible Answers:

\displaystyle m=8

\displaystyle m=4

\displaystyle m=-4

\displaystyle m=16

Correct answer:

\displaystyle m=4

Explanation:

Find the slope of the following linear equation:

\displaystyle 4y-48=16x

We can find the slope by solving this equation for y.

First, add 48 to both sides

\displaystyle 4y=16x+48

Next, divide both sides by 4

\displaystyle y=4x+12

Now, our slope is simply the number attached to our x variable. In this case, it is 4

 

\displaystyle m=4

 

Example Question #841 : Ged Math

Find the x-intercept of the following linear equation:

\displaystyle 4y-48=16x

Possible Answers:

\displaystyle (6,0)

\displaystyle (0,-3)

\displaystyle (-3,0)

\displaystyle (3,0)

Correct answer:

\displaystyle (-3,0)

Explanation:

Find the x-intercept of the following linear equation:

\displaystyle 4y-48=16x

The x-intercept is where a line crosses the x axis. At the x-intercept the y value must be equal to 0.

To find our x-intercept, we are going to plug in 0 for y and solve.

\displaystyle 4(0)-48=16x

\displaystyle -48=16x

Next, divide by 16.

\displaystyle \frac{-48}{16}=x

\displaystyle -3=x

So as an ordered pair, our answer is:

\displaystyle (-3,0)

Example Question #841 : Ged Math

A line on the coordinate plane has slope \displaystyle -1.6. Give the slope of a line parallel to this line.

Possible Answers:

\displaystyle 1.6

\displaystyle 0.625

\displaystyle -1.6

\displaystyle -0.625

Correct answer:

\displaystyle -1.6

Explanation:

Two parallel lines have the same slope, or are both vertical. Since the first line has slope \displaystyle -1.6, a line parallel to this line must have slope \displaystyle -1.6 also.

Example Question #844 : Ged Math

What is the y-intercept of a line that has a slope of \displaystyle \frac{1}{8} and passes through the point \displaystyle (16, 7)?

Possible Answers:

\displaystyle (0, -9)

\displaystyle (0, 4)

\displaystyle (0, -5)

\displaystyle (0, 5)

Correct answer:

\displaystyle (0, 5)

Explanation:

Recall what the slope-intercept form of an equation looks like:

\displaystyle y=mx+b

Start by writing the equation in point-slope form:

\displaystyle y-7=\frac{1}{8}(x-16)

Simplify this equation and re-write it into slope-intercept form.

\displaystyle y-7=\frac{1}{8}x-2

\displaystyle y=\frac{1}{8}x+5

Since the value of \displaystyle b is \displaystyle 5, the y-intercept is located at \displaystyle (0, 5).

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