Question 2 - A-Level Maths

Express $4 ^ { x }$ in terms of $y$, where $y = 2 ^ { x }$.
Hence find the values of $x$ that satisfy the equation $$3 \left( 4 ^ { x } \right) - 10 \left( 2 ^ { x } \right) + 3 = 0 ,$$ giving your answers correct to 2 decimal places.