Advertisements
Advertisements
Question
Expand.
(7x − 9y)3
Sum
Solution
(7x − 9y)3
(a − b)3 = a3 − 3a2b + 3ab2 − b3
= `(7x)^3 - 3 xx (7x)^2 xx (9y) + 3 xx (7x) xx (9y)^2 - (9y)^3`
= `(343x^3) - (3 xx 49x^2 xx 9y) + (21x xx 81y^2) - 729y^3`
= `343x^3 - 1323x^2y + 1701xy^2 - 729y^3`
∴ (7x − 9y)3 = `343x^3 - 1323x^2y + 1701xy^2 - 729y^3`
shaalaa.com
Is there an error in this question or solution?
