Question

Expand:

(4a − 5b − 6)²

Answer 1

(4a − 5b − 6)²

Here, let a = 4a, b = −5b, c = −6

Using the identity,

(a + b + c)² = a² + b² + c² + 2ab + 2bc + 2ca

Thus,

= (4a − 5b − 6)² = (4a)² + (−5b)² + (−6)² + 2(4a)(−5b) + 2(−5b)(−6) + 2(−6)(4a)

= 16a² + 25b² + 36 + 2(−20ab) + 2(−30b) + 2(24ac)

∴ (2a − 3b + 5c)² = 16a² + 25b² + 36 − 40ab + 60b − 48a