Question

Which polynomial can be factored using the binomial theorem?

x2 + 20x + 400
x2 + 45x + 225
x3 – 18x2 + 108x - 36
x3 + 21x2 + 147x + 343

Answer 1

Explanation:

I think the one you want is the last one, but I've never called it that.

21x^2 + 147x + x^3 + 343

x^3 + 343 is a cubic binomial. It factors into (x + 7) (x^2 - 7x + 49)

21x(x + 7) + (x + 7)(x^2 - 7x + 49)

(x + 7) [ 21x - 7x + x^2 + 49)

(x + 7) [x^2 + 14x + 49]

(x + 7) ( x+7)^2

(x + 7)^3

It's the only answer that does factor. There must be a simpler way of doing it, but this will give you the right answer.