设方程x^2-7x+8=0的两根为x1,x2,不解方程求下列代数式的值(1)x1^3-8x1^2+15x1-8(2)(1/(x1-6))-x2/2快啊,不解方程
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/28 22:34:36
![设方程x^2-7x+8=0的两根为x1,x2,不解方程求下列代数式的值(1)x1^3-8x1^2+15x1-8(2)(1/(x1-6))-x2/2快啊,不解方程](/uploads/image/z/14063593-49-3.jpg?t=%E8%AE%BE%E6%96%B9%E7%A8%8Bx%5E2-7x%2B8%3D0%E7%9A%84%E4%B8%A4%E6%A0%B9%E4%B8%BAx1%2Cx2%2C%E4%B8%8D%E8%A7%A3%E6%96%B9%E7%A8%8B%E6%B1%82%E4%B8%8B%E5%88%97%E4%BB%A3%E6%95%B0%E5%BC%8F%E7%9A%84%E5%80%BC%EF%BC%881%EF%BC%89x1%5E3-8x1%5E2%2B15x1-8%EF%BC%882%EF%BC%89%281%2F%28x1-6%29%29-x2%2F2%E5%BF%AB%E5%95%8A%2C%E4%B8%8D%E8%A7%A3%E6%96%B9%E7%A8%8B)
x͒J@_.eSLrH">QC*x*(TLWfDo03?3 xU.SQpyQdâ>PEvzyyM]9foe~CY'z_d@G-ҁtǹDPP~щvo=51SiB-"5-XLsl`\bNfM&t!lVfƃo0$vu°%%O%NVIkwK.2cԞ,G:Mcl P
设方程x^2-7x+8=0的两根为x1,x2,不解方程求下列代数式的值(1)x1^3-8x1^2+15x1-8(2)(1/(x1-6))-x2/2快啊,不解方程
设方程x^2-7x+8=0的两根为x1,x2,不解方程求下列代数式的值
(1)x1^3-8x1^2+15x1-8
(2)(1/(x1-6))-x2/2
快啊,不解方程
设方程x^2-7x+8=0的两根为x1,x2,不解方程求下列代数式的值(1)x1^3-8x1^2+15x1-8(2)(1/(x1-6))-x2/2快啊,不解方程
x1+x2=7 x1x2=8
(1)
x1^3-8x1^2+15x1-8
=x1^3-x1^3x2+(x1+x2+x1x2)x1-x1x2
=x1^3-x1^3x2+x1^2+x1^2x2
=x1^3(1-x2)+x1^2(1+x2)
=x1^2(x1-x1x2+1+x2)
=x1^2(x1+x2-x1x2+1)
=x1^2(7-8+1)
=0
(2)
[1/(x1-6)]-x2/2
=[2-x2(x1-6)]/[2(x1-6)]
=[2-x1x2+6x2]/[2(x1-7+1)]
=[2-8+6x2]/[2(x1-x1-x2+1)]
=6(x2-1)/[2(1-x2)]
=-3