Bexpansion

Question 1

When (1-2x)^p is expanded, the coefficient of x^2 is 40, given P is a positive constant, find the value of P

Answer 1

x^2 coefficient is = to (PC2)(-2x)^2(1^p-2)
PC2(4)(x^2)=40x^2
P!/2!(P-2)! . 4 = 40

cancel factorials

P(P-1)/2 = 10 P^2-P-20=0
P=5