次の計算をし，ア～カに当てはまる数や数式を半角英数字で入力しなさい。

1. \(\displaystyle \frac{1}{2}x^2 y \div (-x) \times4y =\fbox{ア}xy^{\fbox{イ}} \)
2. \(\displaystyle (x^2 y)^2 \div (x^4 y^3) \times (-xy^2) =\fbox{ウ} \)
3. \(\displaystyle 3b^2 \times (-2ab)^2 \div 4ab^3 =\fbox{エ} \)
4. \(\displaystyle -2x^2 \div \left( -\frac{3}{2}x^3 y^2 \right) \times \left( -\frac{3}{4}xy \right)^2 =\frac{\fbox{オ}}{\fbox{カ}} \)