Question

What is the factored form of the binomial expansion 625x4 – 3,000x3y + 5,400x2y2 – 4,320xy3 + 1,296y4?

(5x – 6y)4
(5x + 6y)4
(25x – 36y)2
(25x + 36y)2

Answer 1

(5x – 6y)^4

Explanation:

Given

`625x^4 - 3000x^3y + 5400x^2y^2 - 4320xy^3 + 1296y^4`

Required

The factored form

Solving (a): (5x – 6y)^4

Expand using pascal triangle;

Exponent 4 is represented as: 1 4 6 4 1. So, we have:

`(5x - 6y)^4 = 1 * (5x)^4 + 4 * (5x)^3 * (-6y) + 6 * (5x)^2 * (-6y)^2 + 4 * (5x) * (-6y)^3 + 1 * (-6y)^4`

Expand:

`(5x - 6y)^4 = 1 * 625x^4 + 4 * 125x^3 * (-6y) + 6 * 25x^2 * 36y^2 + 20x * (-216y^3) + 1 * (1296y^4)`

Remove brackets

`(5x - 6y)^4 = 625x^4 - 3000x^3y + 5400x^2y^2 - 4320xy^3 + 1296y^4`

Hence, (a) is correct