Question

Hey can anyone help plz?

Answer 1

We have been given an expression $2\sqrt{28} -5\sqrt{63}$ and we are asked to find correct option from the given choices.

Let us simplify our expression.  

$2\sqrt{28} -5\sqrt{63}$

First of all we will take out perfect squares from our radical.

$2\sqrt{7\cdot4} -5\sqrt{7\cdot9}$

$2\sqrt{4} \cdot\sqrt{7} -5\sqrt{9} \cdot\sqrt{7}$

$2\cdot2\sqrt{7} -5\cdot3\sqrt{7}$  

$4\sqrt{7} -15\sqrt{7}$

$-11\sqrt{7}$

Our expression simplifies to $-11\sqrt{7}$, therefore, option C is the correct choice.