如果x2+x-1=0,求x3+2x2+3.

来源：学生作业帮助网编辑：作业帮时间：2024/05/05 03:40:34

如果x2+x-1=0,求x3+2x2+3.
如果x2+x-1=0,求x3+2x2+3.

如果x2+x-1=0,求x3+2x2+3.
x3+2x2+3
=x(x^2+x-1)+x^2+x+3
=x*0+x^2+x-1+4
=0+0+4
=4

用^2 ^3 分别代表平方立方
X^2 + X - 1 = 0
所以
X^2 = 1 - X
X^3 = X^2 * X = (1-X)*X =X - X^2 = X - (1 - X) = 2X - 1
X^3 + 2X^2 + 3 = 2X-1 + 2*(1-X) + 3 = 1 + 3 = 4

因为x2+x-1=0
所以x^2+x=1
原式=x(x^2+x)+x^2+3
=(x^2+x)+3
=4

4
x2=1-x
代入
=x(x2)+2(x2)+3
=x(1-x)+2(1-x)+3
=x-(1-x)+2-2x+3
=4

x^2=1-x
x^3+2x^2+3
=x^2(x+2)+3
=(1-x)(x+2)+3
=-x^2-x+5
=-(1-x)-x+5
=4

若 x2-3x+1=0,求（2x2×x3-5x2×x2+2 x3-8x2 ）÷（x2+1 ）的值如果x2+x-1=0,求代数式x3+2x2-7的值如果x2+x-1=0,求x3+2x2+3. 已知x2+5x-4=0,求x3+6x2+x+2的值已知x2+x-1=0,求x3+2x2+3的值已知x2-3x+1=0,求x4-6x3+4x2+15x+2 已知x2+x-1=0,求x3+2x2+3的值一道数学题:如果1+x+x2+x3=0,求x+x2+x3+x4+x5+x6+x7+x8的值已知x2+3x2+1=0,求x3+x3分之一+2的值 x2-x-1=0,-x3+2x2+2008= 用MATLAB 求最小值Y= -721.1+678.3*x3+...2184.5*x1.^2-3005.6*x2.^2+44.8*x3.^2-...1974.3*x1.^3+5157.4*x2.^3+...7111.1*x1.*x2.^2+53*x1./x3+2432.6*x2.*x3+-122.9*x2./x3其中X1+X2+X3=1 且都大于0 ,求Y最小值及对应X值.但是我发现算出的如果x2+x-1=0,那么代数式x3+2x2-7的值是【】如果x2+x+1=0,那么代数式x3+2x2-7的值如果x2+x-1=0,那么代数式x3+x2+x2-5的值为多少? 已知x2-3x-1=0求x3-3x2-11x+8的值已知X2-X-1=0求,X5-X4-3X3+3X2+X的值 x2+x-3=0 求x3+3x2-x+2 x2+3x-2=0,求2x3+6x2-4x的值已知x2+x+1=0,求x4+2x3-x2-2x+2014