1) 11x^2 - 6x - 27 = 8x^2 - 6x;
11x^2 - 6x - 27 - 8x^2 + 6x=0
3x^2-27=0
3x^2=27
x^2=9
x=±3
2) 26 + 5y - 0,5y^2 = 2,5y^2 + 26
- 0,5y^2 + 5y + 26 - 2,5y^2 - 26 = 0
-3y^2 + 5y = 0
y(-3y+5)=0
y=0 или -3y+5=0
-3y=-5
y=5\3
3) -7x^2 + 13x + 9 = - 19 + 13x
-7x^2 + 13x + 9 + 19 - 13x = 0
-7x^2 + 28 = 0
-7x^2=-28
x^2=-28\(-7)
x^2=4
x=±2
4) 21z + 11 = 11 + 17z - 5z^2
21z + 11 - 11 - 17z + 5z^2=0
5z^2 + 4z=0
z(5z+4)=0
z=0 или 5z+4=0
5z=-4
z=-0,8