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

Toán Lớp 8: Giúp mình với Rút gọn a)(x-1)×(n+7)-x²+3x b)2x-10+(x-5)×(x+4) c)3x²-(3x-1)×(x+2) d)(x-2)×(x-3)-(x+1)×(x-6)

Tháng Hai 7, 2023 Toán học 2 Comments 0 views

Toán Lớp 8: Giúp mình với
Rút gọn
a)(x-1)×(n+7)-x²+3x
b)2x-10+(x-5)×(x+4)
c)3x²-(3x-1)×(x+2)
d)(x-2)×(x-3)-(x+1)×(x-6)

Comments ( 2 )

  1. diemmyhoa
    diemmyhoa
    7 Tháng Hai, 2023 at 9:40 sáng
    Reply
    a)(x-1)×(n+7)-x²+3x
    =xn+7x-n-7-x²+3x
    =xn+(7x+3x)-n-7x²
    =xn+10x-n-7x²
    b)2x-10+(x-5)×(x+4)
    =2x-10+x²+4x-5x-20
    =x²+(2x+4x-5x)-(10+20)
    =x²+x-30
    c)3x²-(3x-1)×(x+2)
    =3x²-(3x²+6x-x-2)
    =3x²-(3x²+5x-2)
    =3x²-3x²-5x+2
    =-5x+2
    d)(x-2)×(x-3)-(x+1)×(x-6)
    =x²-3x-2x+6-(x²-6x+x-6)
    =x²-3x-2x+6-(x²-5x-6)
    =x²-3x-2x+6-x²+5x+6
    =(x²-x²)-(3x+2x-5x)+(6+6)
    =12

  2. lantrungbach
    lantrungbach
    7 Tháng Hai, 2023 at 9:40 sáng
    Reply
    $\text {a,}$
    (x-1)(n+7)-x^2+3x
    = xn+7x-n-7-x^2+3x
    = -x^2+10x-n+xn-7
    $\text {a,}$
    $\text {→Có thể bạn nhầm đề nên mình làm thêm trường hợp này:}$
    (x-1)(x+7)-x^2+3x
    = x^2+7x-x-7-x^2+3x
    = 9x-7
    $\text {b,}$
    2x-10+(x-5)(x+4)
    = 2x-10+x^2+4x-5x-20
    = x^2+x-30
    $\text {c,}$
    3x^2-(3x-1)(x+2)
    = 3x^2-3x^2-6x+x+2
    = -5x+2
    $\text {d,}$
    (x-2)(x-3)-(x+1)(x-6)
    = x^2-3x-2x+6-x^2+6x-x+6
    =12
    $\text {@lamtung2007}$
     

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

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