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

Toán Lớp 8: a) 2x(x+ 3)−(x−5)(7 + 2x) b) (x^2−1)(x+ 2)−x^2(x+ 2) + 2x

Toán Lớp 8: a) 2x(x+ 3)−(x−5)(7 + 2x)
b) (x^2−1)(x+ 2)−x^2(x+ 2) + 2x

Comments ( 2 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
     a) $2x^{}(x+3)-(x-5)(7+2x)$ 
    = $2x^{2}+6x-(7x-35+2x^2-10x)$ 
    = $2x^{2}+6x-7x+35-2x^2+10x$ 
    = $9x^{}+35$ 
    b) $(x^{2}-1)(x+2)-x^2(x+2)+2x$ 
    = $x^{3}-x+2x^2-2-x^3-2x^2+2x$ 
    = $x^{}-2$ 

  2. $a)2x(x+3)-(x-5)(7+2x)$
    $=2x^{2}+6x-(7x+2x^{2}-35-10x)$
    $=2x^{2}+6x-7x-2x^{2}+35+10x$
    $=9x+35$
    $b)(x^{2}-1)(x+2)-x^{2}(x+2)+2x$
    $=(x^{3}+2x^{2}-x-2)-(x^{3}+2x^{2})+2x$
    $=x^{3}+2x^{2}-x-2-x^{3}-2x^{2}+2x$
    $=x-2$

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

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