1) 4x^2-20xy+4xc
2) -6a^2+18ab-12a
3) 5y^2+25xy-20y
4) 5a+10+a+2=6a+12=6(a+2)
5) x-3-3x+9=-2x+6=2(-x+3)
6) 7x-49-3x+9=4x-40=4(x-10)
7) 2x^2+2x-8x+4x^2=6x^2-6x=6x(x-1)
8) 4xy-6y^2-15y^2+9y^2=-12y^2+4xy=4y(-3y+x)
9) 120x-15-120x-32=-47
10)8-12x+42x+7-81x-36=-51x-21=-3(17x+7)
X²-4x-12=0
D=b²-4ac
D=16+4*1*12
D=16+48
D=64
x1=b+√D÷2a
4+8÷2=12÷2=6
x2=b-√D÷2a
x2=4-8÷2=-2
= 4 * 4 * 4 * 4 * 4 * ( 4 4 4 4 4 4 4 ) / 4 4 4 4 4 4 4 4 4
сверху 7 + 5 снизу 9 четверок
12 - 9 = 3
т.е. 4 * 4 * 4 = 16 * 4 = 64