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Does Excel have the power to solve for x in complex quadratic equations? Please help.

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    Does Excel have the power to solve for x in complex quadratic equations? Please help.

    Hi all,

    As you see in the formula below, there is x in it and I need to compute x when all other values for the variables are known. I have the values of M, W, Icl etc. in specific cells and I want to solve for x so that its value gets calculated and displayed in one cell. So far I have been using computational engines to calculate x, because of which I have to waste a lot of time to go write the value of x manually in the cell each time.

    x=35.7-0.028*(M – W)-Icl*((3.96*10^-8)*fcl*((x + 273)^4 – (Tc + 273)^4)+fcl*hc*(x – Tai))

    Do you have a solution for this? It would be very beneficial for me.

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    Re: Does Excel have the power to solve for x in complex quadratic equations? Please help.

    Is there a part of entering this function into Excel that you don't understand. It should be as easy as:
    1) Enter values for M, W, Icl, etc into cells in Excel.
    2) In the cell for x, enter the formula as outlined, replacing M, W, Icl, etc with references to the cells containing those values. Note that you can enter numbers in scientific notation (3.96*10^-8) as 3.96E-8.
    3) Without writing the whole thing out, it should look something like =35.7-0.028*(A1-A2)-A3*3.96E-8*A4*...

    If you are unfamiliar with creating formulas in Excel, I might suggest an introductory page like this https://support.office.com/en-us/art...e-b50a667eb491
    Quote Originally Posted by shg
    Mathematics is the native language of the natural world. Just trying to become literate.

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    Re: Does Excel have the power to solve for x in complex quadratic equations? Please help.

    Hi Mr. Shorty,

    Thanks for your reply. Sorry maybe I wasn't clear with my question. Let's put it this way -

    Say A1, A2,A3 etc consists the value of M, W, Icl etc .... and I want the value of x to be represented in A10. Therefore, I put in cell A10 my formula as follows =35.7-0.028*(cellA1 – cellA2)-cellA3....., which is x. I do not know the value of x and need it to be computed. So you see my problem? Both the right hand side and left hand side of the equation has x. I want a solution where maybe the RHS doesn't have x.

    I hope I am clearer now.

    Thanks!

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    Re: Does Excel have the power to solve for x in complex quadratic equations? Please help.

    I missed that part of the problem, my apologies.

    Yes, Excel like other programming languages can solve these sorts of problems, and there are several different approaches.

    1) As written, the equation lends itself readily to "successive approximations" or "simple iteration". Choose a value for x, put it in the right side, calculate a new value of x, put that back into the right side, and continue until x is obviously converged or diverging. As part of another question, I created this spreadsheet that illustrates the method of successive approximations: http://www.excelforum.com/excel-form...ate-event.html
    2) There are more robust "root-finding algorithms" as well, and these, too, can be programmed into Excel. I created this spreadsheet and tutorial to illustrate the Newton Raphson and secant methods: http://www.excelforum.com/tips-and-t...ind-roots.html
    3) Solver (and probably Goal Seek) can be used to find roots of equations, too. Enter a guess for x, and your formula in two separate cells. Then instruct Solver to set those two cells equal to each other (or set a cell with their difference equal to 0) by changing x. Solver, by default, uses a NR type algorithm, so it is not very different from (2), but it is sometimes easier for people to tell Solver to solve the equation than to write their own algorithm.

    Sorry about the confusion before, but my answer is still, yes, Excel can be programmed to solve these kinds of equations.

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