Question

Solve for $y$: $\sqrt{7}{y}^2-6y-13\sqrt{7}=0$

• A. $\sqrt{7},2\sqrt{7}$
• B. $3,\frac{2}{\sqrt{7}}$
• C. $\frac{13}{\sqrt{7}},-\sqrt{7}$
• D. None of these

Answer 1

Answer: (C)

$\frac{13}{\sqrt{7}},-\sqrt{7}$

$\sqrt{7}{y}^2-6y-13\sqrt{7}=0$
Therefore
$\sqrt{7}.(-13\sqrt{7})$
$=-91$
Hence
$\sqrt{7}{y}^2-13y+7y-13\sqrt{7}=0$
$y(\sqrt{7}y-13)+\sqrt{7}(\sqrt{7}y-13)=0$
$(y+\sqrt{7})(\sqrt{7}y-13)=0$
$y=-\sqrt{7}$ and $y=\frac{13}{\sqrt{7}}$