$$9{x^2} + 25 - 30x$$    can be expressed as the square of = ?

A. $$3{x^2} - 25$$

B. $$3x + 5$$

C. $$ - 3x - 5$$

D. $$3x - 5$$

Answer: Option D

Solution(By Examveda Team)

$$\eqalign{ & {\text{We have to find}} \cr & = \sqrt {9{x^2} + 25 - 30x} \cr} $$
 $$ = \sqrt {{{\left( {3x} \right)}^2} - 2.3x.5 + {{\left( { - 5} \right)}^2}} $$   $$\,\,\,\,\,\,\,\left\{ {\because {a^2} - 2ab + {b^2} = {{\left( {a + b} \right)}^2}} \right\}$$
$$\eqalign{ & = \sqrt {{{\left( {3x - 5} \right)}^2}} \cr & = 3x - 5 \cr} $$