a1=12d=7n=24⇒a24=a1+23d=12+23∗7=12+161=173S24=2a1+a24∗24=(12+173)∗12=185∗12=2220text\Otvet:a24=173;S24=2220
a1=12d=7n=24⇒a24=a1+23d=12+23∗7=12+161=173S24=2a1+a24∗24=(12+173)∗12=185∗12=2220text\Otvet:a24=173;S24=2220