Answer: Factors to (2x-5)(x-8)
Explanation:
I started by splitting the function into two groups by breaking the -21x into -5x and -16x. Leaving (2x^2 - 5x)(-16x + 40)
From there you want to have matching parenthesis so you pull out a x from the left and -8 on the right. Leaving x(2x-5) -8(2x-5)
Finally simplify to (x - 8)(2x - 5)