Answer:
a = 3
Step-by-step explanation:
Factorize (x+5)(x-4)(x+2)
(x+5)(x-4)(x+2)
= (x²-4x+5x-20)(x+2)
= (x²+x-20)(x+2)
= (x³+2x²+x²+2x-20x-40)
= x³+3x²-18x -40
Compare with x^3+ax^2
3x² = ax²
3 = a
Rearrange
a = 3
Hence the value of a that makes the expressions identical is 3
