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  • If 49x^{2}-b=\left ( 7x + \frac{1}{2} \right )\left ( 7x - \frac{1}{2} \right ) then the valueof b is, (A)0 (B)\frac{1}{\sqrt{2}} (C)\frac{1}{4} (D)\frac{1}{2}

If 49x^{2}-b=\left ( 7x + \frac{1}{2} \right )\left ( 7x - \frac{1}{2} \right ) then the valueof b is,

(A)0   (B)\frac{1}{\sqrt{2}}     (C)\frac{1}{4}     (D)\frac{1}{2}

 

Answers (1)

Given: 49x^{2}-b=\left ( 7x + \frac{1}{2} \right )\left ( 7x - \frac{1}{2} \right )

\left ( 7x + \frac{1}{2} \right )\left ( 7x - \frac{1}{2} \right )=\left ( 7x \right )-\left ( \frac{1}{2} \right )^{2}          \left \{ using (a+b)(a-b)=a^{2}-b^{2} \right \}

Simplifying the given equation we have

\\49x^{2}-b=(7x)^{2}-\left (\frac{1}{2} \right )^{2}\\ 49x^{2}-b=49x^{2}-\frac{1}{4}\\ -b=-\frac{1}{4}\\ b=\frac{1}{4}          

Therefore option (C) is correct.

Posted by

infoexpert24

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