Toán Lớp 8: Bai 8: Phan tich da thuc thanh nhan tu bang phuong phap nhom hang tu:
2. x^2-5x+5y-y^2
3. x^2-2xy+y^2-4z^2
4. x^2-25-2xy+y^2
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Toán Lớp 8: Bai 8: Phan tich da thuc thanh nhan tu bang phuong phap nhom hang tu:
2. x^2-5x+5y-y^2
3. x^2-2xy+y^2-4z^2
4. x^2-25-2xy+y^2
Comments ( 2 )
$2,$ $x^{2}-5x+5y-y^{2}$
$=(x^{2}-y^{2})-(5x-5y)$
$=(x-y)(x+y)-5(x-y)$
$=(x-y)(x+y-5)$
$3,$ $x^{2}-2xy+y^{2}-4z^{2}$
$=(x^{2}-2xy+y^{2})-4z^{2}$
$=(x-y)^{2}-(2z)^{2}$
$=(x-y-2z)(x-y+2z)$
$4,$ $x^{2}-25-2xy+y^{2}$
$=(x^{2}-2xy+y^{2})-25$
$=(x-y)^2-5^{2}$
$=(x-y-5)(x-y+5)$
Giải đáp:
$2) x^2-5x+5y-y^2$
$= (x^2-y^2)-(5x-5y)$
$= (x-y).(x+y)-5.(x-y)$
$= (x-y).(x+y-5)$
$3) x^2-2xy+y²-4z^2$
$= (x^2-2xy+y²)-(4z)^2$
$= (x-y)²-(2z)²$
$ = (x-y+2z).(x-y-2z)$
$4) x^2-25-2xy+y^2$
$= (x²-2xy+y²)-25$
$= (x-y)²-5²$
$= (x-y+5).(x-y-5)$