In the binomial expansion of $(a-b)^n, n \geq 5$, the sum of $5^{ ext {th }}$ and $6^{ ext {th }}$ terms is zero, then $\frac{a}{b}$ equals

Question

In the binomial expansion of $(a-b)^n, n \geq 5$, the sum of $5^{	ext {th }}$ and $6^{	ext {th }}$ terms is zero, then $\frac{a}{b}$ equals

Aicharya · Accepted Answer

${ }^n C_4 a^{n-4}(-b)^4+{ }^n C_5 a^{n-5}(-b)^5=0$ $\Rightarrow\left(\frac{a}{b}\right)=\frac{n-5+1}{5}$.

In the binomial expansion of $(a-b)^n, n \geq 5$, the sum of $5^{\text {th }}$ and $6^{\text {th }}$ terms…