Subject: General Aptitude · Chapter: Square Roots and Cube Roots · Exam: · Marks: · Difficulty:
$9 x^{2}+25-30 x$ can be expressed as the square of [SSC-CHSL (10+2) Exam, 2015]
(a)$3 x^{2}-25$
(b)$3 x-5$
(c)$-3 x-5$
(d)$3 x-5$
Answer
Answer (as printed): D
Explanation
Given $9 x^{2}+25-30 x$ We have to find $\sqrt{9 x^{2}+25-30 x}$ $$\begin{aligned} & =\sqrt{(3 x)^{2}-2.3 x \cdot 5+(-5)^{2}} \quad\left\{\because a^{2}-2 a b+b^{2}=(a-b)^{2}\right\} \\ & =\sqrt{(3 x-5)^{2}}=3 x-5 \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.