Х1*х2=-5
х1 + х2= 7
(9х²1*х2 + 9х1*х²2)/7х1*х2 = 9х1*х2(х1 + х2)/7х1*х2 = 9*7/7 = 9
3x^2 + ax - 72 = 0 / делим обе части уравнения на 3
x^2 + (a/3)*x - 24 = 0
x1*x2 = -24
8*x2 = - 24
x2 = -24/8
x2 = - 3
x1 + x2 = - (- 3 + 8) = - 5
a/3 = - 5
a = - 15
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1) D=256=16 в квадрате
х1= 16:4=4
х2=-16:4=-4
(t-6)^2=t^2 - 12t+ 36
неправильное 1), 2), 4) 5)
правильное 3)