CAT 2022 Slot 3 QA Question & Solution
AlgebraMedium
Question
If $(\sqrt{\frac{7}{5}})^{3x-y}=\frac{875}{2401}$ and $(\frac{4a}{b})^{6x-y}=(\frac{2a}{b})^{y-6x}$, for all non-zero real values of a and b, then the value of $x+y$ is
Solution
$(\sqrt{\frac{7}{5}})^{3x-y}=\frac{875}{2401}$
$\left(\frac{7}{5}\right)^{\frac{\left(3x-y\right)}{2}}=\frac{125}{343}$
$\left(\frac{7}{5}\right)^{\frac{\left(3x-y\right)}{2}}=\left(\frac{7}{5}\right)^{-3}$
3x-y = -6
$(\frac{4a}{b})^{6x-y}=(\frac{2a}{b})^{y-6x}$
Therefor, y=6x as the bases are different so the power should be zero for the results to be equal.
3x-y=-6
or, 3x - 6x = -6
or x= 2
y= 6x = 12
x+y = 14
