the answer is right. its 56
sry my mistake wrong quesrion
If f(x) = (2x+9)^3, f '(x) = 3(2x+9)^2*(2), or f '(x) = 6(2x+9)^2. Here we used the power rule with chain rule to find the derivative.
You already have all you need. Just put in it the slope-intercept form: y=mx+b where m is the slope and b is the y-intercept so
y=7x-4
Area of canvas= 113 square in
area of one side= 113/4=28.22
=28 square in