Answer:
40
Explanation:
(x+2)^5 use binomial theorem :
(a+b)^n = (n choose 0)*a^n*b^0 + (n choose 1)*a^(n-1)*b^1 + (n choose 2)*a^(n-2)*b^2) + ... + (n choose (n-1)*a^1*b^(n-1) + ( n choose n)*a^0*b^n
this seems like a lot but to break it down, notice how the exponent on 'a' decreases as the exponent on 'b' gets bigger.
also, the 'choose' formula is :
(n choose r ) = n!/ (n-r)!r!
now plug in your values
(x+2)^5 =
(5 choose 0)*x^5*2^0 + (5choose 1)*x^4*2^1 + (5 choose 2)*x^3*x^2 + (5 choose 3)*x^2*2^3 + (5 choose 4)*x^1*2^4 + (5 choose 5)*x^0*x^5
we only need the third term so we will solve for this :
(5 choose 2)*x^3*x^2
5 choose 2 = 5!/ (5-2)!2! = 5!/ 3!2! = 10
x^3 * 2^2 = 4x^3
10*4x^3 = 40x^3