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

Toán Lớp 8: rút gọn: a)3.(x+2).(x-2)-(x-5)^2+2.(x+1) b)5.(x-1)^2-(x+5)^2-(2x+3).(2x-3) giúp mik nhanh nhag 3 giờ hôm nay mik hc r

Toán Lớp 8: rút gọn:
a)3.(x+2).(x-2)-(x-5)^2+2.(x+1)
b)5.(x-1)^2-(x+5)^2-(2x+3).(2x-3)
giúp mik nhanh nhag 3 giờ hôm nay mik hc r

Comments ( 2 )

  1. $a)3(x+2)(x-2)-(x-5)^2+2(x+1)$
    $=3(x^2-4)-(x^2-10x+25)+(2x+2)$
    $=3x^2-12-x^2+10x-25+2x+2$
    $=2x^2-35+12x$
    $b)5(x-1)^2-(x+5)^2-(2x+3)(2x-3)$
    $=5(x^2-2x+1)-(x^2+10x+25)-(4x^2-9)$
    $=5x^2-10x+5-x^2-10x-25-4x^2+9$
    $=-20x-11$.

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

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