SAT Math : SAT Mathematics

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #531 : Sat Mathematics

What is the slope-intercept form of \dpi{100} \small 8x-2y-12=0\(\displaystyle \dpi{100} \small 8x-2y-12=0\)?

Possible Answers:

\dpi{100} \small y=4x+6\(\displaystyle \dpi{100} \small y=4x+6\)

\dpi{100} \small y=2x-3\(\displaystyle \dpi{100} \small y=2x-3\)

\dpi{100} \small y=-4x+6\(\displaystyle \dpi{100} \small y=-4x+6\)

\dpi{100} \small y=4x-6\(\displaystyle \dpi{100} \small y=4x-6\)

\dpi{100} \small y=-2x+3\(\displaystyle \dpi{100} \small y=-2x+3\)

Correct answer:

\dpi{100} \small y=4x-6\(\displaystyle \dpi{100} \small y=4x-6\)

Explanation:

The slope intercept form states that \dpi{100} \small y=mx+b\(\displaystyle \dpi{100} \small y=mx+b\). In order to convert the equation to the slope intercept form, isolate \dpi{100} \small y\(\displaystyle \dpi{100} \small y\) on the left side:

\dpi{100} \small 8x-2y=12\(\displaystyle \dpi{100} \small 8x-2y=12\)

\dpi{100} \small -2y=-8x+12\(\displaystyle \dpi{100} \small -2y=-8x+12\)

\dpi{100} \small y=4x-6\(\displaystyle \dpi{100} \small y=4x-6\)

Example Question #5 : How To Find The Equation Of A Line

A line is defined by the following equation:

\(\displaystyle 7x+28y=84\)

What is the slope of that line?

Possible Answers:

\(\displaystyle 28\)

\(\displaystyle 4\)

\(\displaystyle -4\)

\(\displaystyle \frac{1}{4}\)

\(\displaystyle -\frac{1}{4}\)

Correct answer:

\(\displaystyle -\frac{1}{4}\)

Explanation:

The equation of a line is

y=mx + b where m is the slope

Rearrange the equation to match this:

7x + 28y = 84

28y = -7x + 84

y = -(7/28)x + 84/28

y = -(1/4)x + 3

m = -1/4

Example Question #532 : Sat Mathematics

If the coordinates (3, 14) and (5, 15) are on the same line, what is the equation of the line?

Possible Answers:

\(\displaystyle y=\frac{1}{8}x+14.375\)

\(\displaystyle y=-\frac{1}{8}x+14.375\)

\(\displaystyle y=-\frac{1}{8}x+13.625\)

\(\displaystyle y=-8x-38\)

\(\displaystyle y=-8x+38\)

Correct answer:

\(\displaystyle y=-\frac{1}{8}x+14.375\)

Explanation:

First solve for the slope of the line, m using y=mx+b

m = (y2 – y1) / (x2 – x1)

= (15  14) / (5 3)

= (1 )/( 8)

=1/8

y = (1/8)x + b

Now, choose one of the coordinates and solve for b:

14 = (1/8)3 + b

14 = 3/8 + b

b = 14 + (3/8)

b = 14.375

y = (1/8)x + 14.375

Example Question #1 : Coordinate Geometry

What is the equation of a line that passes through coordinates \dpi{100} \small (2,6)\(\displaystyle \dpi{100} \small (2,6)\) and \dpi{100} \small (3,5)\(\displaystyle \dpi{100} \small (3,5)\)?

Possible Answers:

\dpi{100} \small y=2x+4\(\displaystyle \dpi{100} \small y=2x+4\)

\dpi{100} \small y=3x+2\(\displaystyle \dpi{100} \small y=3x+2\)

\dpi{100} \small y=x+7\(\displaystyle \dpi{100} \small y=x+7\)

\dpi{100} \small y=-x+8\(\displaystyle \dpi{100} \small y=-x+8\)

\dpi{100} \small y=2x-4\(\displaystyle \dpi{100} \small y=2x-4\)

Correct answer:

\dpi{100} \small y=-x+8\(\displaystyle \dpi{100} \small y=-x+8\)

Explanation:

Our first step will be to determing the slope of the line that connects the given points.

\(\displaystyle m=\frac{y_2-y_1}{x_2-x_1}=\frac{6-5}{2-3}=\frac{1}{-1}=-1\)

Our slope will be \(\displaystyle -1\). Using slope-intercept form, our equation will be \(\displaystyle y=(-1)x+b\). Use one of the give points in this equation to solve for the y-intercept. We will use \dpi{100} \small (2,6)\(\displaystyle \dpi{100} \small (2,6)\).

\(\displaystyle 6=(-1)(2)+b\)

\(\displaystyle 6=-2+b\)

\(\displaystyle 8=b\)

Now that we know the y-intercept, we can plug it back into the slope-intercept formula with the slope that we found earlier.

\(\displaystyle y=(-1)x+8\)

\(\displaystyle y=-x+8\)

This is our final answer.

Example Question #11 : How To Find The Equation Of A Line

Which of the following equations does NOT represent a line?

Possible Answers:

\(\displaystyle x=10\)

\(\displaystyle 5y=10\)

\(\displaystyle x-y=10\)

\(\displaystyle x+y=10\)

\(\displaystyle x^2+y=10\)

Correct answer:

\(\displaystyle x^2+y=10\)

Explanation:

The answer is \(\displaystyle x^2+y=10\).

A line can only be represented in the form \(\displaystyle x=z\) or \(\displaystyle y=mx+b\), for appropriate constants \(\displaystyle z\), \(\displaystyle m\), and \(\displaystyle b\). A graph must have an equation that can be put into one of these forms to be a line.

\(\displaystyle x^2+y=10\) represents a parabola, not a line. Lines will never contain an \(\displaystyle x^2\) term.

Example Question #14 : How To Find The Equation Of A Line

Let y = 3x – 6.

At what point does the line above intersect the following:

\(\displaystyle 2x =\frac{2}{3}y+4\)

 

 

Possible Answers:

(0,–1)

They intersect at all points

(–5,6)

They do not intersect

(–3,–3)

Correct answer:

They intersect at all points

Explanation:

If we rearrange the second equation it is the same as the first equation. They are the same line.

Example Question #531 : Geometry

Find the equation of a line that goes through the points \(\displaystyle (0,3)\), and \(\displaystyle (-10,4)\).

Possible Answers:

\(\displaystyle y=-\frac{1}{10}x+3\)

\(\displaystyle y=-\frac{1}{10}x\)

\(\displaystyle y=-10x+3\)

\(\displaystyle y=-10x\)

\(\displaystyle y=-13x\)

Correct answer:

\(\displaystyle y=-\frac{1}{10}x+3\)

Explanation:

For finding the equation of a line, we will be using point-slope form, which is

\(\displaystyle y-y_0=m(x-x_0)\), where \(\displaystyle m\) is the slope, and \(\displaystyle (x_0, y_0)\) is a point. 

\(\displaystyle m=\frac{y_2-y_1}{x_2-x_1}=\frac{4-3}{-10-0}=\frac{1}{-10}=-\frac{1}{10}\)

We will pick the point \(\displaystyle (0,3)\)

\(\displaystyle y-3=-\frac{1}{10}(x-0)\)

\(\displaystyle y=-\frac{1}{10}x+3\)

If we picked the point \(\displaystyle (-10,4)\)

 

\(\displaystyle y-4=-\frac{1}{10}(x+10)\)

\(\displaystyle y=-\frac{1}{10}x-1+4\)

\(\displaystyle y=-\frac{1}{10}x+3\)

We get the same result

Example Question #533 : Sat Mathematics

Find the equation of a line that passes through the point \(\displaystyle (-2,5)\), and is parallel to the line \(\displaystyle y=-3x+4\).

Possible Answers:

\(\displaystyle y=-3x\)

\(\displaystyle y=-3x-1\)

\(\displaystyle y=-3x-10\)

\(\displaystyle y=-3x+1\)

\(\displaystyle y=-3x-3\)

Correct answer:

\(\displaystyle y=-3x-1\)

Explanation:

Since we want a line that is parallel, we will have the same slope as the line \(\displaystyle (-3)\). We can use point slope form to create an equation.

\(\displaystyle y-y_0=m(x-x_0)\), where \(\displaystyle m\) is the slope and \(\displaystyle (x_0, y_0)\) is a point.

\(\displaystyle y-5=-3(x-(-2))\)

\(\displaystyle y-5=-3(x+2)\)

\(\displaystyle y-5=-3x-6\)

\(\displaystyle y=-3x-1\)

Example Question #25 : Geometry

Find the equation of the line shown in the graph below:

 

 Sat_math_164_05

 
Possible Answers:

y = -1/2x - 4

y = 2x + 4

 y = -1/2x + 4

y = x/2 + 4

Correct answer:

y = x/2 + 4

Explanation:

Based on the graph the y-intercept is 4. So we can eliminate choice y = x/2 - 4.

The graph is rising to the right which means our slope is positive, so we can eliminate choice y = -1/2x + 4.

Based on the line, if we start at (0,4) and go up 1 then 2 to the right we will be back on the line, meaning we have a slope of  (1/2).

Using the slope intercept formula we can plug in y= (1/2)x + 4.

 

 

Example Question #1 : How To Find The Length Of A Line With Distance Formula

What is the distance between (1, 4) and (5, 1)?

Possible Answers:

5

7

9

3

4

Correct answer:

5

Explanation:

Let P1 = (1, 4) and P2 = (5, 1)

Substitute these values into the distance formula: 

Actmath_29_372_q6_1_copy

The distance formula is an application of the Pythagorean Theorem:  a2 + b2 = c2

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