3.
6x^2-18x=0;
6x(x-3)=0;
x=0 и x=3
4.
2a(5a-4)-(a-8)(a-5)=10a^2-8a-a^2+8a+5a-40=9a^2+5a-40
5.a)
(2x+9)/4-(x-2)/6=3;
(3(2x+9)-2(x-2))/12=3;
6x+27-2x+4=36;
4x+31=36;
4x=5;
x=5/4=1,25
5.б)
(4x-3)(x+7)=(2x-4)(2x+5)+3;
4x^2-3x+28x-21=4x^2-8x+10x-20+3;
4x^2+25x-21=4x^2+2x-17;
25x-21=2x-17;
23x=21-17;
x=4/23.
6.
18*0+6*(5/3)-24*0-8=10-8=2.