CAT 2017 Ratio, Proportion and Variation — Previous Year Question

If $a$ and $b$ are integers of opposite signs such that $(a + 3)^2 : b^2 = 9 : 1$ and $(a - 1)^2 : (b - 1)^2 = 4 : 1$, then the ratio $a^2 : b^2$ is: