Toán Lớp 8: (x+1)^2-(x-1)^2-3(x+1)(x-1) giúp mìnhvs
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Toán Lớp 8: (x+1)^2-(x-1)^2-3(x+1)(x-1) giúp mìnhvs
Comments ( 2 )
=(x^2+2x+1)-(x^2-2x+1)-3.(x^2-1^2)
=x^2+2x+1-x^2+2x-1-3.(x^2-1)
=x^2+2x+1-x^2+2x-1-3x^2+3
=(x^2-x^2-3x^2)+(2x+2x)+(1-1+3)
=-3x^2+4x+3