Question

1) 3х в квадрате + 6х = 8х в квадрате -15х
2) 10x+7х в квадрате=2х в квадрате +8х
3)х(х-15)=3умножить (108-5х)

Answer 1

$1) \: 3{x}^{2} + 6x = 8 {x}^{2} - 15x \\ - 5 {x}^{2} + 21x = 0 \\ x( - 5x + 21) = 0 \\ x = 0 \: \: \: ulu \: \: \: - 5x + 21 = 0 \\ ....................5x = 21 \\ ....................x = 4.2 \\ 2) \: 10x + 7 {x}^{2} = 2 {x}^{2} + 8x \\ 2x + 5 {x}^{2} = 0 \\ x(5x + 2) = 0 \\ x = 0 \: \: ulu \: \: 5x + 2 = 0 \\ ................x = - 0.4 \\ 3) \: x(x - 15) = 3(108 - 5x) \\ {x}^{2} - 15x = 324 - 15x \\ {x}^{2} = 324 \\ x = + - \sqrt{324} \\ x = + - 18$