I agree, you would use the formula, "y=mx+b" to solve this graph. First, you find to exact points within the graph. In this case, you have (0,0) (-2-,16), and (2,16).
So choosing two out of these points, you will solve for "m", which is your slope. In order to find the slope, you will use the y1-y2 over x1-x2 formula.
[I chose the two points (-2, -16) and (2, 16)]:
16-(-16) 32
---------- = ------
2-(-2) 4
Taking this fraction, you will simplify it to 8. (Since 4 can go into 32, eight times)
Now that you have your slope, substitute it into your "y=mx+b" equation where m is:
y=8x+b
Though, you don't have your b, your y-intercept, so you can either insert one of your two points you used to find slope OR you can find where the line intersects along the y-axis.
Solving process for "b", using the point (2, 16):
y=8x+b
16=8(2)+b --> SUBSTITUTE the points into it's perspective slots/places.
16=16+b --> SUBTRACT, so that b is isolated.
-16 -16
-----------
0=b --> This is your y-intercept.
So your final answer all together for the graph is: y=8x+0