For which value of x on the graph of 𝑓 (𝑥) = (x+1)(x+2) is parallel to the line 3𝑥 − 𝑦 − 5 = 0

Question

For which value of x on the graph of 𝑓 (𝑥) = (x+1)(x+2) is parallel to the line 3𝑥 − 𝑦 − 5 = 0
a. −1 
b. 1 
c. 3 
d. 0

Reiny · Answer

f(x) = (x+1)(x+2) = x^2 + 3x + 2 f'(x) = 2x + 3 <---- the slope of the tangent at any value of x the slope of your given line is 3 so 2x+3 = 3, solve for x and you are done