Toán Lớp 8: có thể giúp mik ko mik đang cần gấp!!! a)x^2-(a+b)x+ab b)x^2-2x-4y^2-4y c)x^4+2x^3-4x-4 d)x^2-y^2-2x-2y

Question

Toán Lớp 8:  có thể giúp mik ko mik đang cần gấp!!! a)x^2-(a+b)x+ab b)x^2-2x-4y^2-4y c)x^4+2x^3-4x-4 d)x^2-y^2-2x-2y

tuanh · Answer

a)     $x^2-(a+b)x+ab$     $=x^2-ax-bx+ab$     $= left(x^2-ax right)- left(bx-ab right)$     $=x left(x-a right)-b left(x-a right)$     $= left(x-a right) left(x-b right)$     b)     $x^2 - 2x - 4y^2 - 4y$     $= (x^2 - 4y^2) - (2x + 4y)$     $= (x + 2y)(x - 2y) - 2(x + 2y)$     $= (x + 2y)(x - 2y - 2)$     $= (x + 2y)[x - 2(y + 1)]$     c)     $x^4+2x^3-4x-4   =x^4-2x^2+2x^3-4x+2x^2-4   =x^2 left(x^2-2 right)+2x left(x^2-2 right)+2 left(x^2-2 right)   = left(x^2-2 right) left(x^2+2x+2 right)$     d)     $x^2-y^2-2x+2y$     $= left(x^2-y^2 right)- left(2x-2y right)$     $= left(x-y right) left(x+y right)-2 left(x-y right)$     $= left(x-y right) left(x+y-2 right)$

diepbich93 · Answer

a) x^2 - ( a + b )x + ab   = x^2 - ax - bx + ab   = x( x - a ) - b ( x - a )   = ( x - b )( x - a )   b) x^2 - y^2 - 2x - 2y   = ( x^2 - 4y^2 ) - ( 2x + 4y )   = [( x^2 - (2y)^2] - 2( x + 2y )   = ( x - 2y )( x + 2y ) - 2( x + 2y )   = ( x - 2y - 2 )( x + 2y )   c) x^4 + 2x^3 - 4x - 4   = (x^2 - 2)(x^2 + 2) + 2x(x^2 - 2)   = (x^2 - 2)(x^2 + 2x + 2)   d) x^2 - y^2 - 2x - 2y  = (x-y)(x+y)-2(x-y)   =(x-y)(x+y-2)