解方程5x³+2X²+2x+1=147
问题描述：
解方程5x³+2X²+2x+1=147
答
5x³ + 2X² + 2x + 1 = 147
5x³ + 2X² + 2x - 146 = 0 (1)
x^3 + 0.4x^2 + 0.4x - 29.2 = 0 (2)
只能用迭代法作近似计算：
x = (29.2 - 0.4x^2 - 0.4x)^(1/3)
取 x0 = 2.9110，误差 ε = 0.0001
x1 = 2.91015
x1 = 2.91024
x1 = 2.91023
得出第一个根：
x(1) ≈ 2.9102
从(2) 中去掉(x - 2.9102)的因子，余项为：
x^2 + 3.3102 x + 10.0333 = 0
B^2 - 4AC x(2) = ( - 3.3102 + i √29.1757)/2
x(3) = ( - 3.3102 - i √29.1757)/2
答
f(x)=5x^3+2x^2+2x-146
f(3)=13>0
f(2)=-94