SAT Mathematics Practice Test 7

Applying the distributive property, the original expression is equivalent to $5+12\mathit{i}\mathit{–}9{\mathit{i}}^2+6\mathit{i}$. Since $\mathit{i}=\sqrt{-1}$, it follows that ${\mathit{i}}^2=-1$. Substituting –1 for ${\mathit{i}}^2$ into the expression and simplifying yields $5+12\mathit{i}+9+6\mathit{i}$, which is equal to $14+18\mathit{i}$.