12a
3(2x²-3x)=4(x²+2x)
6x²-9x=4x²+8x
2x²-17x=0, x(2x-17)=0, x=0, x=17/2
12c
5(2x-3)²=2(22,5-4x)
5(4x²-12x+9)=45-8x
20x²-60x+45=45-8x
20x²-52x=0, 4x(5x-13)=0, x=0, x=13/5
13a
(3x-2)(x+3)=(x+2)(x-3)
3x²+9x-2x-6=x²-3x+2x-6
2x²+10x=0, 2x(x+5)=0, x=0, x=-5
13b
[(x-2)²+(x+2)²]/(x²-4)=10/3
3(x²-4x+4+x²+4x+4)=10x²-40
6x²+24=10x²-40
4x²--64=0, x²-16=0, x=4, x=-4
