1. (2y+7)(7-2y)+6y²=49+7y
49-4y²+6y²=49+7y
2y²=7y
y1=0
2y2=7
y2=3,5
2. (1+5x)(5x-1)-10(x-2)=19
25x²-1-10x+20=19
25x²-10x=0
5x(5x-2)=0
x1=0
5x2=2
x2=0,4
3. (8x+5)^2+64x²=80x+123
64x²+80x+25+64x²=80x+123
128x²=98
64x²=49
(8x²)=7²
8x=±7
x=±7/8
x1=-7/8
x2=7/8
4. 3x²-4x+4=-2(2x-4-x²)
3x²-4x+4=-4x+8+2x²
x²=4
x=±2
x1=-2
x2=2