解方程: x²-7x-18=0的公式法解题过程-搜答案-搜搜做题作业网

x(x^2-2)+2x^2(x+3)-3x(5x-7)=x(3x^2-9x+17)+2=>x^3-2x+2x^3+6x^2-15x^2+21x=3x^3-9x^2+17x+2=>2x=2x=1

x³+3x²+3x-7=0x³-x²+4x²+3x-7=0x²(x-1)+(x-1)(4x+7)=0(x-1)(x²+4x+7)=

x^4-2x^3+2x^3-4x^2-3x^2+6x-2x+4=0x^3(x-2)+2x^2(x-2)-3x(x-2)-2(x-2)=0(x-2)(x^3+2x^2-3x-2)=0x=2;

【解法一】【解法二】5x(x+7)(x+4)=5x(x^2+11X)5x(x²+11x+28)-5x(x²+11x)=05x^3+55x^2+140x=5x^3+55x^25x(x

只有一个实根.设f(x)=x^3+2x-19为单调增函数.所以只有一个实根.下面来求这个实根由于f(2)=-7f(3)=11所以这个根在（2,3）内.利用二分法求这个解.取x0=5/2f(5/2)=1

x^2-|x|=0当x≥0,x^2-x=0x(x-1)=0x=0,x=1当x

2x²-7x=0x²-7/2+49/16=49/16（x-7/4）²=49/16x-7/4=+,—7/4x=0,x=7/8

intf(floatx)返回值,错了.

7x^2+2x＝0x﹙7x+2﹚=0∴x=0或﹙7x+2﹚=0∴x1=0x2=-2／7

4x^2(x+2)-9(x+2)=0(x+2)(4x^2-9)=0(x+2)(2x-3)(2x+3)=0x=-2,1.5,-1.5

简单的分类讨论：x²-4x+8=0,无解【b²-4ac＜0】一般c太大,都是无解的、x²-4x=0,x1=4x2=0即为最终答案、楼主!

x^4-4x^3-4x^2+15x+18=0x^4-3x^3-x^3+3x^2-7x^2+21x-6x+18=0(x-3)(x^3-x^2-7x-6)=0x1=3x2=3.49449283705542

（x+1)/(x+2)+(x+6)/(x+7)=(x+2)/(x+3)+(x+5)/(x+6)(x+2-1)/(x+2)+(x+7-1)/(x+7)=(x+3-1)/(x+3)+(x+6-1)/(x+

(x+x)+(x-x)+(xx)+(x/x)=1002x+0+x²+1=100x²+2x+1=100（x+1）²=10²x+1=10或x+1=-10x=9或x=

X^4-7X^2+4X+4=x^4-2x^3+2x^3-4x^2-3x^2+6x-2x+4=x^3(x-2)+2x^2(x-2)-3x(x-2)-2(x-2)=(x-2)(x^3+2x^2-3x-2)

x^6+x^5(-1-3)+x^4(-4+3+1)+x^3(7+12-1-2)+x^2(-21-4+2)+x(7+8)-14+6x^2-15x+18=0x^6-4x^5+16x^3-17x^2+4=0

用求根公式即可.5/2x²-48/7x+2=035x²-96x+28=0x=(96+/-√(96²-4*35*28))/(2*35)=(48+/-2√331)/35再问：