Equations of Lines

Write the equation of a line that has a slope of 9 and a y-intercept of

 $\left(0,-\frac{1}{2}\right)$  

•  $y=-\frac{1}{2}x-9$  

•  $y=\frac{1}{2}x-9$  

•  $y=9x-\frac{1}{2}$  

•  $y=-9x-\frac{1}{2}$  

Answer explanation

the slope is always multiplied with the variable X

Tags

CCSS.8.EE.B.6

CCSS.8.F.A.3

What is the value of m in the equation? Use the graph.

 $y=m\ x+3$  

•  $3$  

•  $-3$  

•  $\frac{1}{3}$  

•  $-\frac{1}{3}$  

Answer explanation

This line falls so the slope is negative. It falls 3, runs 1 from one point to the next:  -3/1 reduces to -3.

Tags

CCSS.8.F.B.4

CCSS.HSF.LE.A.2

Find the POINT-SLOPE FORM equation of the line that passes through the point (-3,8) and has a slope of -4.

•  $y+8=-4\left(x-3\right)$  

•  $y-8=-4\left(x+3\right)$  

•  $y+3=-4\left(x-8\right)$  

•  $y-3=-4\left(x+8\right)$  

SHOW YOUR WORK!  Write a slope-intercept equation of the line that passes through the point and has the given slope:

 $\left(9.-6\right)$   $slope:\ m=\frac{2}{3}$  

•  $y=\frac{2}{3}x$  

•  $y=\frac{2}{3}x-12$  

•  $y=\frac{2}{3}x-13$  

•  $y=\frac{2}{3}x+13$  

Answer explanation

start by using point-slope form!

Write the equation in slope-intercept form of a line that passes through:

 $\left(10,-12\right)\ and\ \left(6,-4\right)$  

•  $y=-2x+8$  

•  $y=2x-8$  

•  $y=-2x-8$  

•  $y=-4x+20$  

Answer explanation

First find the slope, then pick one of the points and substitute it into the point-slope formula.

 $\left(-2,-9\right)\ and\ \left(1,\ -9\right)$  

SHOW YOUR WORK!! Write the equation of the line that passes through the points.

•  $zero$  

•  $undefined$  

•  $y=-9$  

•  $x=-9$  

Answer explanation

the slope of this line is zero, which means that it is a horizontal line and horizontal lines have equations that look like this:  y = #

Which equation represents the line below?

• $y=2x$

• $y=2$

• $x=2$

• $x=-3$

Answer explanation

this is a vertical line so the equation is always in the form: x = #
*pay attention WHERE the line intersect the x-axis

What is the equation of the line?

• $y=-3x$

• $y=-3$

• $x=-3$

• $x=0$

Answer explanation

This is a horizontal line. Horizontal lines always have equations that look like this: y = #
*look @ where the line intersects the y-axis!

Which of these are true about the line below?

• the line is rising and has a positive slope

• the line is falling and has a negative slope

• the y-intercept is negative

• the y-intercept is positive

Answer explanation

this line has a positive slope of 3/2 (rise/run) and a y-intercept of (0,-4)

Tags

CCSS.8.EE.B.5

 $\left(8.-7\right)\ \ \ \ \ \ \ m=-\frac{1}{4}$  

SHOW YOUR WORK! 

What is the slope-intercept equation of the line?

•  $y=-\frac{1}{4}x-7$  

•  $y=-\frac{1}{4}x-5$  

•  $y=-\frac{1}{4}x-9$  

•  $y=-\frac{1}{4}x-6$  

Answer explanation

use point-slope to begin!

Tags

CCSS.8.EE.B.6

CCSS.8.F.A.3