f'(x)= [tex]\frac{18tx+20x-7x^{2} +63t+140}{(x^{2} +9t+20)^{2} }[/tex]
Answer: f'(x)= x+r=9 over 2 x 7 = 126
because 9 x 2 = 18 x 7= 126
your answer is 126
Step-by-step explanation:
