A3+A7=24
A3×A7=128
Найти d; a1; A5; S8

a1+2d+a1+6d=24⇒2a1+8d=24⇒a1+4d=12⇒a1=12-4d(a1+2d)(a1+6d)=128(12-4d+2d)(12-4d+6d)=128(12-2d)(12+2d)=128144-4d²=1284d²=144-1284d²=16d²=41)d1=-2a1=12+8=20a5=a1+4d=12S8=(2a1+7d)*8/2S8=(40-14)*4=26*4=1042)d=2a1=12-8=4S8=(8+14)*4=22*4=88