Question

If $3x+\frac{2}{x}=7$, then $\left(9x^2-\frac{4}{x^2}\right)=$

(a) 25

(b) 35

(c) 49

(d) 30

Answer 1

We have to find the value of

Given

Using identity we get,

Here

Substituting we get,

By transposing left hand side we get,

Again using identity we get,

Substituting we get

Using identity we get

Here

Substituting we get,

The value of is

The correct choice is (b)