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#1
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Looking to reverse a quadratic formula, Sqrt and all??
I know there is a trend line avail. with poly fit and you can change to
numbers. However when reversing this formula to solve for X there is no help in excel. Is there an add in or someone whith a spreadsheet that can help? Simple Quadratic help would do? |
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#2
Posted to microsoft.public.excel.misc
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Looking to reverse a quadratic formula, Sqrt and all??
with the usual coefficients:
a in A1 b in B1 c in C1 use: =(-B1+(B1*B1-4*A1*C1)^0.5)/(2*A1) =(-B1-(B1*B1-4*A1*C1)^0.5)/(2*A1) For for A1 thru C1: 10 60 30 the formulas return the Real roots: -0.550510257 -5.449489743 For non-Real roots you must use more "imaginative" methods. -- Gary''s Student - gsnu200860 "DataSchemer" wrote: I know there is a trend line avail. with poly fit and you can change to numbers. However when reversing this formula to solve for X there is no help in excel. Is there an add in or someone whith a spreadsheet that can help? Simple Quadratic help would do? |
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#3
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Looking to reverse a quadratic formula, Sqrt and all??
Use the quadratic formula
with A in A1, b in B1, c in C1 =-b +/- sqrt(b**2-4ab) __________________ 2a =IF(B1^2-(4*A1*B1)=0,(-1*B1)+SQRT(B1^2-(4*A1*B1))/(2*A1),(-1*B1/2*A1)&"+"&SQRT((4*A1*B1)-B1^2)/(2*A1)&"i") and =IF(B1^2-(4*A1*B1)=0,(-1*B1)-SQRT(B1^2-(4*A1*B1))/(2*A1),(-1*B1/2*A1)&"-"&SQRT((4*A1*B1)-B1^2)/(2*A1)&"i") "DataSchemer" wrote: I know there is a trend line avail. with poly fit and you can change to numbers. However when reversing this formula to solve for X there is no help in excel. Is there an add in or someone whith a spreadsheet that can help? Simple Quadratic help would do? |
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#4
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Looking to reverse a quadratic formula, Sqrt and all??
To calculate non real roots:
Real1: =(-B1+IF(B1^2-4*A1*C1<0,0,B1^2-4*A1*C1)^0.5)/(2*A1) Imaginary1 (if needed): =IF(B1^2-4*A1*C1<0,(-1*(B1^2-4*A1*C1))^0.5/(2*A1),"") Real2: =(-B1-IF(B1^2-4*A1*C1<0,0,B1^2-4*A1*C1)^0.5)/(2*A1) Imaginary2 (if needed): =IF(B1^2-4*A1*C1<0,(-1*(B1^2-4*A1*C1))^0.5/-(2*A1),"") -- Best Regards, Luke M *Remember to click "yes" if this post helped you!* "Gary''s Student" wrote: with the usual coefficients: a in A1 b in B1 c in C1 use: =(-B1+(B1*B1-4*A1*C1)^0.5)/(2*A1) =(-B1-(B1*B1-4*A1*C1)^0.5)/(2*A1) For for A1 thru C1: 10 60 30 the formulas return the Real roots: -0.550510257 -5.449489743 For non-Real roots you must use more "imaginative" methods. -- Gary''s Student - gsnu200860 "DataSchemer" wrote: I know there is a trend line avail. with poly fit and you can change to numbers. However when reversing this formula to solve for X there is no help in excel. Is there an add in or someone whith a spreadsheet that can help? Simple Quadratic help would do? |
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