Toán Lớp 8: 6) y^2 (x^2 + y) − zx^2 − zy
7) x^3 + 8 + 6x(x + 2)
8) (5x − 4)^2 − 49x^2
9) x^2– 2xy + y^2 – xz + yz
10) 3 – 9x + 9x^2– 3x^3
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Toán Lớp 8: 6) y^2 (x^2 + y) − zx^2 − zy
7) x^3 + 8 + 6x(x + 2)
8) (5x − 4)^2 − 49x^2
9) x^2– 2xy + y^2 – xz + yz
10) 3 – 9x + 9x^2– 3x^3
Comments ( 2 )
= y^2(x^2 + y) – (zx^2 + zy).
= y^2(x^2 + y) – z(x^2 + y).
= (x^2 + y)(y^2 – z).
7, x^3 + 8 + 6x(x + 2)
= (x^3 + 2^3) + 6x(x + 2).
= (x + 2)(x^2 – 2x + 4) + 6x(x + 2).
= (x + 2)(x^2 – 2x + 4 + 6x).
= (x + 2)(x^2 + 4x + 4).
= (x + 2)(x + 2)^2.
8, (5x – 4)^2 – 49x^2
= (5x – 4 + 7x)(5x – 4 – 7x)
9, x^2 – 2xy + y^2 – xz + yz
= (x^2 – 2xy +y^2) – z(x – y)
= (x – y)^2 – z(x – y)
= (x – y)(x – y – z)
= y^2(x^2 + y) – (zx^2 + zy).
= y^2(x^2 + y) – z(x^2 + y).
= (x^2 + y)(y^2 – z).
7, x^3 + 8 + 6x(x + 2)
= (x^3 + 2^3) + 6x(x + 2).
= (x + 2)(x^2 – 2x + 4) + 6x(x + 2).
= (x + 2)(x^2 – 2x + 4 + 6x).
= (x + 2)(x^2 + 4x + 4).
= (x + 2)(x + 2)^2.
8, (5x – 4)^2 – 49x^2
= (5x – 4 + 7x)(5x – 4 – 7x)
( áp dụng hđt thứ ba ).
9, x^2 – 2xy + y^2 – xz + yz
= (x^2 – 2xy +y^2) – z(x – y)
= (x – y)^2 – z(x – y)
= (x – y)(x – y – z)
10, câu sai đề à bạn, check giúp mình nhé.
mình đang trục trặc xíu nên trình bày kí hiệu nhìn hơi rối, thông cảm nhé.
@nieucacvan.