x2 + 5x - 6 = 0
D = b2 - 4ac
D = 25 + 24 = 49 = 7^2
x1,2 = -b ± √D/2a
x1 = -5 + 7/2 = 2 /2= 1
x2 = -5 - 7/2 = - 12/2 = -6
ответ: x1 = 1; x2 = -6
x2 - 1.3x + 2 = 0
D = b2 - 4ac
D = 1.6900000000000002 - 8 = -6.31 < 0
ответ: нет решений
x2 - 8x - 84 = 0
D = b2 - 4ac
D = 64 + 336 = 400 = 20^2
x1,2 = -b ± √D/2a
x1 = 8 + 20/2 = 28/2 = 14
x2 = 8 - 20/2 = - 12/2 = -6
ответ: x1 = 14; x2 = -6
36x2 - 12x + 1 = 0
D = b2 - 4ac
D = 144 - 144 = 0
x = - b/2a
x = 12/72= 1/6
ответ: x = 1/6
3x2 + 32x + 80 = 0
D = b2 - 4ac
D = 1024 - 960 = 64 = 8^2
x1,2 = -b ± √D/2a
x1 = -32 + 8/6= - 24/6 = -4
x2 = -32 - 8/6 = - 40/6= - 20/3
ответ: x1 = -4 ; x2 = - 20/3
5x2 + 26x - 24 = 0
D = b2 - 4ac
D = 676 + 480 = 1156 = 34^2
x1,2 = -b ± √D/2a
x1 = -26 + 34/10= 8 /10= 4/5
x2 = -26 - 34/10= - 60/10 = -6
ответ: x1 = 4/5 ; x2 = -6
S=20+35=55*30=1650:2=825cm2