Question

An equivalent expression with a rational denominator is...

Answer 1

Given the expression,

$(8x-56x^2)/(\sqrt{14x-2})$

We will have to rationalize the denominator first. To rationalize the denominator we have to multiply the numerator and denominator both by the square root part of the denominator.

$[(8x-56x^2)(\sqrt{14x-2})]/[(\sqrt{14x-2})(\sqrt{14x-2})]$

If we have $(\sqrt{a})(\sqrt{a})$, we will get $\sqrt{a^2}$ by multiplying them. And $\sqrt{a^2} = a$.

So here in the problem, we will get,

$[(8x-56x^2)(\sqrt{14x-2})]/(14x-2)$

Now in the numerator we have $(8x-56x^2)$. We can check 8x is common there. we will take out -8x from it, we will get,

$-8x(-1+7x)$

$-8x(7x-1)$

And in the denominator we have $14x-2$. We can check 2 is common there. If we take out 2 from it we will get,

$2(7x-1)$

So we can write the expression as

$[(-8x)(7x-1)(\sqrt{14x-2})]/[2(7x-1)]$

$(7x-1)$ is common to the numerator and denominator both, if we cancel it we will get,

$(-8x)(\sqrt{14x-2})/2$

We can divide -8 by the denominator, as -8 os divisible by 2. By dividing them we will get,

$(-4x)(\sqrt{14x-2})$

$(-4x)(14x-2)^(1/2)$

So we have got the required answer here.

The correct option is the last one.