(a(i))[3]
Given that $y = 2^x$, show that $2^x + 3(2^{-x}) = 4$ can be expressed as $y^2 - 4y + 3 = 0$.
(a(ii))[3]
Hence Solve the equation $2^x + 3(2^{-x}) = 4$, giving the values of $x$ to $3$ significant figures where appropriate.
Mathematics 9709 · AS & A Level · Logarithmic and exponential functions