4x^2-0,64=(2x-0,8)(2x+0,8) 36a^2b^2-81/100x^2=(6ab-9/10x)(6ab+9/10x) (x-y)^2-(a-b)^2=(x^2-2xy+y^2)-(a^2-2ab+b^2) (x+y)^2-(y+a)^2=(x^2+2xy+y^2)-(y^2+2ya+a^2)=x^2+2xy-2ya-a^2 0.09a^2-0.25b^2=(0.3a-0.5b)(0.3a+0.5b) (3x-y)^2-9y^2=(9x^2-3xy+y^2)-9y^2=9x^2-3xy-8y^2