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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 8: a/(x+2)(x-1) b/(a+b)³ -(a-b)³ -6a²b c/x(x-1) d/(y+2x)(2x-y) Giúp em với ạ!!

Toán Lớp 8: a/(x+2)(x-1)
b/(a+b)³ -(a-b)³ -6a²b
c/x(x-1)
d/(y+2x)(2x-y)
Giúp em với ạ!!

Comments ( 1 )

  1. $a)(x+2)(x-1)$
    $=x^2-x+2x-2$
    $=x^2+x-2$
    $b)(a+b)^3-(a-b)^3-6a^2b$
    $=a^3+3a^2b+3ab^2+b^3-(a^3-3a^2b+3ab^2-b^3)-6a^2b$
    $=a^3-3a^2b+3ab^2+b^3-a^3+3a^3b-3ab^2+b^3$
    $=2b^3$
    $c)x(x-1)$
    $=x^2-x$
    $d)(y+2x)(2x-y)$
    $=(2x+y)(2x-y)$
    $=(2x)^2-y^2$
    $=4x^2-y^2$
    Chúc bạn học tốt !!!!

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222-9+11+12:2*14+14 = ? ( )