(a-b)²=a²-2ab+b²
a²-b²=(a-b)(a+b)
16-24y+9y²=4²-2*4*3y+3²y²=(4-3y)²=(4-3y)(4-3y)
[tex]9(a-b)-c^2=3^2 (\sqrt{a-b} )^2-c^2=(3\sqrt{a-b})^2-c^2= \\ =(3\sqrt{a-b}-c)(3\sqrt{a-b}+c)[/tex]
3x²-30x+75=3(x²-10x+25)=3(x²-2*x*5+5²)=3(x-5)²=3(x-5)(x-5)
15xy²+5xy-20x²y=5xy(3y+1-4x)
3a²-3b²-a+b=3(a²-b²)-(a-b)=3(a-b)(a+b)-(a-b)=(a-b)(3(a+b)-1)=(a-b)(3a+3b-1)
