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?