Примерно за 4.3 часа. Я так посчитал, могу ошибатся
671-14=657
657/9=73
На 73 делили число
P=2(x+y)=80
S1=x*y
S2=(x+8)(y+2)
S2/S1=1.5,
(x+8)(y+2) / (x*y) = 3/2 (1)
x+y=40
x=40-y, 2*(40-y+8)(y+2)=3*y*(40-y)
(80-2y+16)(y+2)=120y-3y^2
80y+160-2y^2-4y+16y+32-120y+3y^2=0, y^2-28y+192=0, y1=16, y2=12
y1=16, x1=24
y2=12, x2=28
S1=16*24=384, S1'=12*28=336
S2=(24+8)(16+2)=576, S2'=(28+8)(12+2)=504
Ответ:
5x≥0 x≥0
7-2x≥0 2x≤7 x≤3.5
x∈[0;3.5]
Аn = а1 + (n - 1)d ===> d = (an - a1) / (n - 1)
d = (39 -3) / (11 - 1)
d = 36/10
d = 3.6