Solving for x given F(x) for nonlinear polynomial function
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Hello my name is Sara I have a polynomial function that looks like this:
kp = {(1-b)^3/b^2}*{20/5-b}
I have the value for kp but I need to solve for b.
How can I do this in matlab.
Please help
Thank you
回答（1 个）
Walter Roberson
2011-7-11
b = roots([1, -7, 15-kp, -13, 4])
3 个评论
bym
2011-7-11
I didn't know that roots would solve for exponents less than 1. Unless I a missing something I get for the expansion of kp:
4/b^2 - 13/b - 7*b + b^2 + 15
Can you clarify? Thanks
Walter Roberson
2011-7-12
kp = (1-b)^3/b^2*(4-b)
Multiply both sides by b^2 (assuming b is non-zero)
kp * b^2 = (1-b)^3*(4-b)
Expand the right hand side
kp * b^2 = 4-13*b+15*b^2-7*b^3+b^4
move the left side to the right to get
0 = 4-13*b+(-kp+15)*b^2-7*b^3+b^4
Reorder by descending powers of b, take the coefficients and write the roots() expression.
bym
2011-7-13
doh! :(
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