Question

FAN+MEDAL
Which equation represents the graph of the linear function?



A.
y = −3x + 1

B.
y = −3x − 1

C.
y = 3x + 1

D.
y = 3x − 1

Answer 1

Please help!

Answer 2

You can see the y-intercept below the x-axis is (0,-1) and another point on the line is (1,2) find the slope using:
\[(y _{2}-y _{1})/(x _{2}-x _{1})\]
With these two points and then use y=mx+b form with b being the y intercept and m being the slope found using the formula above.

Answer 3

Stillll dont know how to solve it...

Answer 4

Which part is giving you trouble? Is it the y-intercept or finding the slope?

Answer 5

Uhh both actually.

Answer 6

I do not know how to find the slope.

Answer 7

Okay, so the y-intercept is where the line hits the y-axis. For straight lines, it will only touch the y-axis in one place unless it is a vertical line on the axis. In this case, you can see by inspection that the y-intercept is (0,-1) as that is the point where the line hits the axis.

To find the slope, you use the formula I gave above with two points, each having a distinct x and y value. In this case, I picked the first point to be the y-intercept which we found to be (0,-1). I also picked the point (1,2) by inspection because it is an easy point to work with on the line. So:
Point 1: \[(x _{1}, y _{1})=(0, -1)\]
Point 2: \[(x _{2}, y _{2})=(1, 2)\]

Now using the slope formula above you can plug in the values of \[x _{1}, x _{2}, y _{1}, y _{2}\] to solve for the slope like so:
(2-(-1))/(1-0)=(2+1)/1=3

Now use the formula y=mx+b to give the equation of the line, where m is the slope we just calculated and b is the y-intercept (0,-1) we found by looking at the graph of the line. Hope that clears it up!

Answer 8

Oh ok, so C?

Answer 9

Since your y-intercept is (0,-1) b=-1. So the answer would be D.

The value of b is equal to the value of y at the y-intercept.