Question

解不等式：（2x-3)(x+4)-(x+2)(x-2)>x^2+7

Answer 1

解不等式：（2x-3)(x+4)-(x+2)(x-2)>x^2+7

2x²+8x-3x-12-x²+4＞x²+7;

5x＞15;

x＞3;

已知x^2-3x+1=0,计算下列算式的值：

2x^3-3x^2-7x+2014

=2x(x²-3x)+3x²-7x+2014

=2x×(-1)+3x²-7x+2014

=3x²-9x+2014

=3(x²-3x)+2014

=-3+2014

=2011;

已知xy/x+y=2,

1/x+1/y=1/2;

yz/y+z=4,

1/y+1/z=1/4;

zx/z+x=3,

1/z+1/x=1/3;

1/x-1/y=1/12;

2/x=7/12;

x=24/7;

y=24/5;

z=24;

7x+5y-2z

=24+24-48

=0;

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