x的平方减去7x等于18-搜答案-智慧作业帮

再问：再答：字模糊再问：

3×5½

得到:X^2-15X=-56X^2-15X+56=0(x-7)(x-8)=0所以X=7或者x=8

x^2+3x-1=0(x+3/2)^2-13/4=0(x+3/2+√13/2)(x+3/2-√13/2)=0x=-3/2-√13/2或x=√13/2-3/2

5/3和13/6

x-1/x=3x^2-3x-1=0(1)(1)*x得：x^3-3x^2-x=0(2)(1)*2得：2x^2-6x-2=0(3)(2)+(3)得：x^3-x^2-7x-2=0所以：x^3-x^2-7x+

由2x^2-3x-4=0得：x^2-2=3x/2所以x-2/x=(x^2-2)/x=(3x/2)/x=3/2

x^2+x-1=0x^3+x^2-x=0x^3+2x^2=x^2+x=1x^3+2x^2-7=1-7=-6

x=9

(x^2-2x)/(x^2-x-6)≥1(x^2-2x)/(x^2-x-6)-1≥0{(x^2-2x)-(x^2-x-6)}/(x^2-x-6)≥0(x^2-2x-x^2+x+6)/(x^2-x-6)

x^2-x-1=0(x-1/2)^2=5/4x=1/2±√5/2

答：x^2-2x=150(x-1)^2=151x-1=√151或者x-1=-√151所以：x=1+√151或者x=1-√151

x²-x=-2x²-x+2=0b²-4ac=1-8＜0∴原方程无实数解

十字相乘分解因式2-927得到:(2x-9)(2x+7)=0x1=4.5x2=-3.5

x+y-7=-6x^2-x=13y^2-y=13两式相减x^2-y^2-x+y=0(x+y)(x-y)-(x-y)=0(x-y)(x+y-1)=0因为x≠y所以x-y≠0所以x+y-1=0x+y-7=

因为x^2-4=0,所以x^2=4,所以x（x+1)^2-x(x^2+x)-x+7=x(x^2+2x+1)-x^3-x^2-x+7=x^3+2x^2+x-x^3-x^2-x+7=x^2+7=4+7=1

x^2-10x+24=x^2-4x-6x+24=(x^2-4x)-(6x-24)=x(x-4)-6(x-4)=(x-6)(x-4)

等于x(x-1)

x²-3x=1,利用配方法:x²-3x+9/4=1+9/4(x-3/2)²=13/4x-3/2=±√13/2x=(3±√13)/2也可以用求根公式法解:x²-3