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

Toán Lớp 8: Tìm x, biết: a) (x + 3)2 + (4 – x)(4+x)=7 b) x2 + 2x – 3=0

Tháng Chín 5, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: Tìm x, biết:
a) (x + 3)2 + (4 – x)(4+x)=7
b) x2 + 2x – 3=0

Comments ( 1 )

  1. hoquyly
    hoquyly
    5 Tháng Chín, 2022 at 3:32 sáng
    Reply
    a,(x + 3)2 + (4 – x)(4+x)=7
    ⇔ 2x+6+ 16-x²=7
    ⇔ 2x-x²+15=0
    ⇔ -x²-3x+5x+15=0
    ⇔ -x(x+3)+5(x+3)=0
    ⇔ (x+3)(5-x)=0
    ⇔\(\left[ \begin{array}{l}x=-3\\x=5\end{array} \right.\) 
    b, x²+2x-3=0
    ⇔ x²-x+3x-3=0
    ⇔ x(x-1)+3(x-1)=0
    ⇔ (x+3)(x-1)=0
    \(\left[ \begin{array}{}x=-3\\x=1\end{array} \right.\) 

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

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