GED Math : Standard Form

Study concepts, example questions & explanations for GED Math

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Example Questions

Example Question #1 : Standard Form

Which of the following is an example of an equation of a line written in standard form?

Possible Answers:

\displaystyle \small 2x+4y=7

\displaystyle \small 2x+4y-7=0

\displaystyle \small x=-2y+\frac{7}{2}

\displaystyle \small y=\frac{1}2x+\frac{7}{4}

Correct answer:

\displaystyle \small 2x+4y=7

Explanation:

The standard form of a line is \displaystyle \small Ax+By=C, where all constants are integers, i.e. whole numbers.

Therefore, the equation written in standard form is \displaystyle \small 2x+4y=7.

Example Question #2 : Standard Form

Line

Refer to the above red line. What is its equation in standard form?

Possible Answers:

\displaystyle 2x - y = 8

\displaystyle 2x+ y = 8

\displaystyle 2x+ y = -8

\displaystyle 2x - y = -8

Correct answer:

\displaystyle 2x - y = -8

Explanation:

First, we need to find the slope of the above line. 

Given two points, \displaystyle (x_{1}, y_{1}), (x_{2}, y_{2}), the slope can be calculated using the following formula:

\displaystyle m = \frac{y_{2}-y_{1}}{x_{2}-x _{1}}

Set \displaystyle x_{1}=-4, y_{1}=x_{2}= 0, y_{2}=8:

\displaystyle m = \frac{8-0}{0-(-4)} = \frac{8}{4} = 2

Second, we note that the \displaystyle y-intercept is the point \displaystyle (0,8)

Therefore, in the slope-intercept form of a line, we can set \displaystyle m = 2 and \displaystyle b = 8:

\displaystyle y = mx+b

\displaystyle y = 2x+8

Since we are looking for standard form - that is, \displaystyle Ax+By = C - we do the following:

\displaystyle y - y - 8 = 2x+8 - y - 8

\displaystyle -8 = 2x -y

or 

\displaystyle 2x - y = -8

Example Question #3 : Standard Form

Write the following equation in standard form:

\displaystyle y=-3x+2

Possible Answers:

\displaystyle x=-\frac{1}{3}y+\frac{2}{3}

\displaystyle 3x+y-2=0

\displaystyle y=-3x+2

\displaystyle 3x+y=2

Correct answer:

\displaystyle 3x+y=2

Explanation:

Standard form of an equation is

\displaystyle Ax+By=C.

Rearrange the given equation to make it look like the above equation as follows:

\displaystyle y=-3x+2

\displaystyle y+3x=-3x+3x+2

\displaystyle y+3x=2

\displaystyle 3x+y=2

 

Example Question #4 : Standard Form

Rewrite the following equation in standard form.

\displaystyle 2+4y=3x+10

Possible Answers:

\displaystyle 3x-4y=-8

\displaystyle 4y=3x+8

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

\displaystyle 6y=13x

\displaystyle x=\frac{4}{3}y-\frac{8}{3}

Correct answer:

\displaystyle 3x-4y=-8

Explanation:

The standard form of a line is \displaystyle Ax+By=C, where \displaystyle A, B, \textup{and}\textup{ } C are integers. 

We therefore need to rewrite \displaystyle 2+4y=3x+10 so it looks like \displaystyle Ax+By=C.

The steps to do this are below:

\displaystyle 2+4y=3x+10 \textup{ (subtract 10 from both sides)}

\displaystyle -8 +4y=3x\textup{ (subtract 4y from both sides)}

 \displaystyle -8=3x-4y\ (\textup{flip the two sides of the equality})

\displaystyle 3x-4y=-8

Example Question #5 : Standard Form

Rewrite the equation in standard form:  \displaystyle y=3x+8

Possible Answers:

\displaystyle \textup{The equation is already in standard form.}

\displaystyle -3x-y =8

\displaystyle -3x+y =8

\displaystyle 3x+y =8

\displaystyle -3x+y =-8

Correct answer:

\displaystyle -3x+y =8

Explanation:

To rewrite in standard form, we will need the equation in the form of:

\displaystyle Ax+By =C

Subtract \displaystyle 3x on both sides.

\displaystyle y-3x=3x+8-3x

Regroup the variables on the left, and simplify the right.

The answer is:  \displaystyle -3x+y =8

Example Question #6 : Standard Form

Rewrite the equation in standard form.

\displaystyle y-2=3(x+6)

Possible Answers:

\displaystyle -3x+y = 20

\displaystyle 3x-y = 16

\displaystyle -3x+y = 16

\displaystyle -3x+y = -20

\displaystyle 3x+y = 16

Correct answer:

\displaystyle -3x+y = 20

Explanation:

The given equation is in point-slope form.

The standard form is:  \displaystyle Ax+By = C

Distribute the right side.

\displaystyle y-2=3x+18

Subtract \displaystyle 3x on both sides.

\displaystyle y-2-3x=3x+18-3x

\displaystyle -3x+y-2 = 18

Add 2 on both sides.

\displaystyle -3x+y-2+2 = 18+2

The answer is:  \displaystyle -3x+y = 20

Example Question #5 : Standard Form

Rewrite the equation in standard form:  \displaystyle 3+y-9x=4

Possible Answers:

\displaystyle 9x-y = -7

\displaystyle 9x-y = 7

\displaystyle 9x-7y = -1

\displaystyle 9x-y = -1

\displaystyle -9x-y = 7

Correct answer:

\displaystyle 9x-y = -1

Explanation:

The standard form of a linear equation is:  \displaystyle Ax+By =C

Reorganize the terms.

Add \displaystyle 9x on both sides.

\displaystyle 3+y-9x+(9x)=4+(9x)

\displaystyle 3+y= 4+9x

Subtract \displaystyle y on both sides.

\displaystyle 3+y-y= 4+9x-y

\displaystyle 3= 4+9x-y

Subtract four on both sides.

\displaystyle 3-4= 4+9x-y-4

The answer is:  \displaystyle 9x-y = -1

Example Question #8 : Standard Form

Given the slope of a line is \displaystyle 2 and a point is \displaystyle (4,-3), write the equation in standard form.

Possible Answers:

\displaystyle 2x-y = -11

\displaystyle -2x+3y = -11

\displaystyle -2x+y = -11

\displaystyle -2x+y = -22

\displaystyle 2x-2y = -11

Correct answer:

\displaystyle -2x+y = -11

Explanation:

Write the slope-intercept form of a linear equation.

\displaystyle y=mx+b

Substitute the point and the slope.

\displaystyle -3 = (2)(4)+b

Solve for the y-intercept, and then write the equation of the line.

\displaystyle -3 = 8+b

\displaystyle -3-8 = 8+b-8

\displaystyle b=-11

\displaystyle y=2x-11

The equation in standard form is:  \displaystyle Ax+By =C

Subtract \displaystyle 2x from both sides.

\displaystyle y-2x=2x-11-2x

The answer is:  \displaystyle -2x+y = -11

Example Question #9 : Standard Form

Which of the following is NOT in standard form?

Possible Answers:

\displaystyle \textup{All equations are represented in standard form.}

\displaystyle y=5x^2-3x+5

\displaystyle y-2=3(x+9)

\displaystyle 15x-y=15

\displaystyle -19x+y = 3

Correct answer:

\displaystyle y-2=3(x+9)

Explanation:

The equation in standard form of a linear equation is:  

\displaystyle Ax+By =C

The equation in standard form of a parabolic equation is:  

\displaystyle y= Ax^2+Bx+C

All of the following equations are in standard form except:

\displaystyle y-2=3(x+9)

This equation is in point-slope format:  \displaystyle y-y_1 = m(x-x_1)

The answer is:  \displaystyle y-2=3(x+9)

Example Question #10 : Standard Form

Write the following equation in standard form.

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

Possible Answers:

\displaystyle 3x-y = -7

\displaystyle -3x+y = -7

\displaystyle x-3y = -7

\displaystyle 3x-y = -11

\displaystyle 3x+2y =8

Correct answer:

\displaystyle -3x+y = -7

Explanation:

The standard form of a linear equation is:  \displaystyle Ax+By =C

Distribute the right side.

\displaystyle y-2 = 3x-9

Subtract \displaystyle 3x on both sides.

\displaystyle y-2 -(3x)= 3x-9-(3x)

\displaystyle -3x+y-2 = -9

Add 2 on both sides.

\displaystyle -3x+y-2+2 = -9+2

The answer is:  \displaystyle -3x+y = -7

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