Toán Lớp 8: phân tích đa thức thành nhân tử 1) x^2-3x+xy-3y 2) x^2+y^2-2xy-25 3) 5x^3y+40y 4) 16x^2+8xy+y^2-16 5) 3x^2+14x-15 6) 3xy-6x

Question

Toán Lớp 8:  phân tích đa thức thành nhân tử 1) x^2-3x+xy-3y 2) x^2+y^2-2xy-25 3) 5x^3y+40y 4) 16x^2+8xy+y^2-16 5) 3x^2+14x-15 6) 3xy-6x

minhtamnguyet88 · Answer

Giải đáp:   1)   x^(2)-3x+xy-3y   =x(x-3)+y(x-3)   =(x-3)(x+y)   2)   x^(2)+y^(2)-2xy-25   =x^(2)-2xy+y^(2)-25   =(x-y)^(2)-5^2   =(x-y-5)(x-y+5)   3)   5x^(3)y+40y   =5y.x^(3)+5y.8   =5y.(x^(3)+8)   =5y(x+2)(x^(2)-2x+4)   4)   16x^(2)+8xy+y^(2)-16   =[(4x)^(2)+2.4x.y+y^2]-16   =(4x+y)^(2)-4^2   =(4x+y-4)(4x+y+4)   5)   3x^(2)+14x-15   (Sai đề)   6)   3xy-6x   =3x.y-3x.2   =3x.(y-2)

hienthucthu97 · Answer

$Giải đáp+Lời giải và giải thích chi tiết:$      $1) x&sup2;-3x+xy-3y$                     $2) x&sup2;+y&sup2;-2xy-25$     $= (x&sup2;+xy)-(3x+3y)$                 $= (x&sup2;-2xy+y&sup2;)-25$     $= x.(x+y)-3.(x+y)$                   $= (x-y)&sup2;-5&sup2;$     $= (x-3).(x+y)$                           $= (x-y-5).(x-y+5)$     $3) 5x&sup3;y+40y$                          $4) 16x&sup2;+8xy+y&sup2;-16$     $= 5y.(x&sup3;+8)$                             $= (16x&sup2;+8xy+y&sup2;)-16$     $= 5y.(x+2).(x&sup2;-2x+4)$             $= (4x+y)&sup2;-4&sup2;$                                                             $ = (4x+y-4).(4x+y+4)$     $5) 3x&sup2;+14x-15$                      $6) 3xy-6x$     $=  3x&sup2;+9x+5x-15$                   $= 3x.(y-2)$     $= (3x&sup2;+9x)+(5x-15)$     $= 3x.(x+3)+5.(x-3)$     $= 3x.(x+3)-5.(x+3)$     $= (3x-5).(x+3)$     $@festivals$