Question

What is the 7th term of `(c-d)^10`?

Answer 1

`7` th term is `210 *c^4*d^6`

Explanation:

`(a + b)^n =(nC_0) a^nb^0+ (nC_1) a^(n-1)b^1 +(nC_2) a^(n-2)b^2 +...... (nC_n)b^n`
Here `(a=c ; b=-d , n= 10)`

We know `nC_r= (n!)/(r!(n-r)!) :. 10C_6=210`

`7` th term is `(10C_6)c^(10-6)*(-d)^6 =210 c^4*d^6`

`7` th term is `210 *c^4*d^6` [Ans]