bantu jawab dong,smg yg bantu rezekinya lancarrr

i. [tex]28*14 - \pi 7^2 = 392 - 49 \pi[/tex] cm
ii.[tex] \frac{1}{4} \pi(10)^2 = 25\pi[/tex] cm
iii.[tex]21^2+ \frac{1}{2}\pi( \frac{21}{2})^2 = 441+ \frac{441}{8}\pi [/tex] cm
iv. kurang jelas