Question

solve
4^x-3(2^x)=40

Answer 1

\[\begin{align*}4^x-3(2^x)&=40\\
(2^2)^x-3(2^x)&=40\\
(2^x)^2-3(2^x)&=40\\
\end{align*}\]
take \[y=2^x\] then,
\[y^2-3y=40\implies y^2-3y-40=0\]
now it's a simple quadratic equation solve for y and find x from it.