bantuin yah soalnya di kumpulin besok plis ^_^

[tex]4a) \: \: \pi( {3}^{2} - {2}^{2} ) = 5\pi \\ 4b) \: \: \frac{1}{2} \times (12 \times 7 + \pi {6}^{2} ) = 42 + 18\pi \\ 4c) \: \: (12 \times 15) + \frac{1}{2} \pi {6}^{2} - \pi {3}^{2} = 180 + 18\pi - 9\pi = 180 - 9\pi \\ 4d) \: \: \frac{1}{4} \times \pi {7}^{2} - \frac{1}{2} \times {7}^{2} = \frac{49\pi}{4} - \frac{49}{2} [/tex]