Toán Lớp 8: 7x(x-4)-(7x+3) (2$x^{2}$ -x+4)
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Toán Lớp 8: 7x(x-4)-(7x+3) (2$x^{2}$ -x+4)
Comments ( 2 )
=(7x.x-7x.4)-(7x.2x²-7x.x+7x.4+3.2x²-3.x+3.4)
=7x.x-7x.4-7x.2x²+7x.x-7x.4-3.2x²+3x-3.4
=7x²-28x-14x³+7x²-28x-6x²+3x-12
=(7x²+7x²-6x²)-(28x+28x-3)-14x³-12
=x²(7+7-6)-(28+28-3)x-14x³-12
=8x²-53x-14x³-12
=-14x³+8x²-53x-12
Vậy 7x(x-4)-(7x+3)(2x²-x+4)=-14x³+8x²-53x-12