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

Toán Lớp 8: Chứng minh a (a+b)^2+(a-b)^2=2(a^2+b^2) b (a+b)^2-(a-b)^2=4ab

Toán Lớp 8: Chứng minh
a (a+b)^2+(a-b)^2=2(a^2+b^2)
b (a+b)^2-(a-b)^2=4ab

Comments ( 1 )

  1. $a)VT=(a+b)^2+(a-b)^2$
                $=a^2+2ab+b^2+a^2-2ab+b^2$
                $=2a^2+2b^2$
                $=2(a^2+b^2)=VP$
    =>đpcm
    $b)VT=(a+b)^2-(a-b)^2$
                $=a^2+2ab+b^2-a^2+2ab-b^2$
                $=4ab=VP$
    =>đpcm

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