Question

expand using binomial therorem

Answer 1

Answer:

(1−2x)3=1−6x+12x2−8x3

Explanation:

We know (a+b)n=nC0an⋅b0+nC1an−1⋅b1+nC2an−2⋅b2+..........+nCnan−n⋅bn

Here a=1,b=−2x,n=3 We know, nCr=n!r!⋅(n−r)!

∴3C0=1,3C1=3,3C2=3,3C3=1

∴(1−2x)3

=3C0⋅13+3C1⋅12⋅(−2x)+3C2⋅1⋅(−2x)2+3C3⋅(−2x)3

∴(1−2x)3=1−6x+12x2−8x3 [Ans]