1)
9x + 21 - 10x + 45 = 0
-x = -66
x = 66
2) 6x(x² - 81) = 0
x² - 81 = 0
x² = 81
x = 9
x1 = 0
x2 = 9
3) 4x² + 4x + 1 - 3x² + 30x - 75 = x² - 9 + 3
4x² + 4x + 1 - 3x² + 30x - 75 - x² + 9 - 3 = 0
4x + 1 + 30x - 75 + 9 - 3 = 0
34x = 68
x = 2
1)= -3 целых 1/6
2) = -6 целых 1/10
3) =-3 целых 43/102
4)=-4целых 1/8