A curve has the equation $y = ab^x$, where $a$ and $b$ are constants and $b > 0$. The curve passes through the points $(1, 10)$ and $(3, 40)$. Find the values of $a$ and $b$.
Mark scheme and worked answer
- M1 for setting up the equations $ab = 10$ and $ab^3 = 40$.
- M1 for dividing the equations to eliminate $a$: $b^2 = 4$.
- A1 for stating $b = 2$ (since $b > 0$).
- A1 for finding $a = 5$.