Question

Find the value of the expression (36x² + 25y² − 60xy), when $x=\frac{2}{3}$ and $y=\frac{1}{5}.$

Answer 1

$$\begin{gathered} \left(36x^2+25y^2-60xy\right) \\ \Rightarrow x=\frac{2}{3},y=\frac{1}{5} \\ ={\left(6x\right)}^2+{\left(5y\right)}^2-2\left(6x\right)\left(5y\right) \\ ={\left(6x-5y\right)}^2 \\ ={\left(6\left(\frac{2}{3}\right)-5\left(\frac{1}{5}\right)\right)}^2 \\ ={\left(4-1\right)}^2 \\ ={\left(3\right)}^2 \\ \Rightarrow 9 \end{gathered}$$