Toán Lớp 8: Chứng minh rằng :
$x^{2}$ + $y^{2}$+$z^{2}$+2xy-2yz-2zx = ( x+y-z)$^{2}$
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Toán Lớp 8: Chứng minh rằng :
$x^{2}$ + $y^{2}$+$z^{2}$+2xy-2yz-2zx = ( x+y-z)$^{2}$
Comments ( 2 )
$VT=(x+2xy+y^2)-2yz-2zx+z^2$
$VT=(x+y)^2-2z(x+y)+z^2$
$VT=(x+y-z)^2=VP(đpcm)$