Question

If $49x^2-b=(7x+\frac{1}{2})(7x-\frac{1}{2})$, then the value of $b$ is :

• A. $0$
• B. $\frac{1}{\sqrt{2}}$
• C. $\frac{1}{4}$
• D. $\frac{1}{2}$

Answer 1

Answer: (C)

$\frac{1}{4}$

$(7x+\frac{1}{2})(7x-\frac{1}{2})=49x^2-b$
$\Rightarrow 49x^2-\frac{1}{4}=49x^2-b$ ($\because (a-b)(a+b)=a^2-b^2$)
$\Rightarrow b=\frac{1}{4}$
Option C is correct.