Solving for x given F(x) for nonlinear polynomial function

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

Answer 1

[Walter Roberson]

b = roots([1, -7, 15-kp, -13, 4])

[bym]

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]

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]

doh! :(