5x^2 + 3x - 8 = 0
D = 3^2 - 4 * 5 * (-8) = 169
√D = √169 = 13
x1 = (-3 + 13) / 10 = 10 / 10 = 1
x2 = (-3 - 13) / 10 = -16 / 10 = -8 / 5
проверка:
1.
5*(1)^2 + 3*(1) - 8 = 0
5 + 3 - 8 = 0
0 = 0
2.
5*(-8 / 5)^2 + 3(-8 / 5) - 8 = 0
5 * (64/25) - 3(8/5) - 8 = 0
64/5 - 24/5 - 8 = 0
((64 - 24) / 5) - 8 = 0
40/5 - 8 = 0
8 - 8 = 0
0 = 0
Ответ: 1, -8/5.
2x^2 + 18x = 0
2x(x + 9) = 0
2x = 0 ⇒ x = 0
x + 9 = 0 ⇒ x = -9
проверка:
1.
2*(0)^2 + 18*0 = 0
0 + 0 = 0
0 = 0
2.
2*(-9)^2 + 18*-9 = 0
2 * 81 - 18 * 9 = 0
162 - 162 = 0
0 = 0
Ответ: 0, -9.