The coefficient of the x^3 term in the expansion of (3x + a)^4 is 216. Find the value of a.
From the binomial theorem we know that the x^3 term in the expansion of the above expression must satisfy,
4C3 * (3x)^3 * a = 216x^3.
Hence, after multiplying out we must have,
108a * x^3 = 216x^3
and therefore the value of a must be 2.
AB
Answered by Adam B. • Further Mathematics tutor
6805 Views
See similar Further Mathematics GCSE tutorsRelated Further Mathematics GCSE answers
All answers ▸Use differentiation to show the function f(x)=2x^3–12x^2+25x–11 is an increasing function for all values of x
Given f(x)= 8 − x^2, solve f(3x) = -28
Work out the coordinates for the stationary point of y = x^2 + 3x + 4
A straight line passes trough the points A(-4;7); B(6;-5); C(8;t). Use an algebraic method to work out the value of t.