Question

Find the coefficient of x⁵ in the expansion of (1 + x)³ (1 – x)⁶ .

Answer 1

To Find : coefficient of x⁵ 

For (1+x)³ 

a=1, b=x and n=3

We have a formula,

By using this formula, we get, ×

Coefficients of x⁵ are 

x⁰ .x⁵ = 1× (-6)=-6 

x¹ .x⁴ = 3×15=45 

x² .x³ = 3×(-20)=-60 

x³ .x² = 1×15=15 

Therefore, Coefficients of x⁵ = -6+45-60+15 = -6 

Conclusion : Coefficients of x⁵ = -6