Solver could not find a feasible solution

[MrFuz]

Can someone help me using solver? solver says there is no feasible solution but I know there is. I’ve tried messing around with different solver methods and the options of solver but still can’t get it to work.

the two equations are:
x^2 * Y - 10^5 = 0
(3*Y) - (2*X) = 0

can someone try using solver to find values of X and Y? And send the file or a screensho?
(I have tried to upload an excel file or a picture but it doesn’t work.)

 

[MrFuz]

What are start guesses? And how would I use that?

Ive used some positive numbers like 5 and 1 and I got an answer but they are not the correct values for X and Y. Because if I change the constraint values then that changes the whole equation as now it would be equal to 5 rather than equal to 0 from the initial equations.

(btw, you are really helpful, thanks)

 

[MrFuz]

What are start guesses? And how would I use that?

Ive used some positive numbers like 5 and 1 and I got an answer but they are not the correct values for X and Y. Because if I change the constraint values then that changes the whole equation as now it would be equal to 5 rather than equal to 0 from the initial equations.

(btw, you are really helpful, thanks)

nevermind, i have got the right answers by changing to positive values for x and y. but how does that work? i thought constraint values has do be 0 here because my equations equalled to 0.

What values do you think I would need to use for the 10^12 question

 

[StephenCrump]

i thought constraint values has do be 0 here because my equations equalled to 0.

You're solving for x and y. The constraints are that your two formulae both evaluate to zero. But you're not constraining x and y.

What values do you think I would need to use for the 10^12 question

Given x^2 * y = N, and y = 2/3 x, a logical first guess would set x and y both equal to N^(1/3).

For N = 10^12, that means starting with x = y = 10,000. Then, Solver easily converges on the answers x = 11,447 and y = 7,631 (approx).

In my version of Excel, Solver will also find the correct solution starting with x and y as small as 10. But set them both to 1, and it will fail to find a solution. So a bit of trial and error might be required with your start values.

 

[MrFuz]

You're solving for x and y. The constraints are that your two formulae both evaluate to zero. But you're not constraining x and y.

Given x^2 * y = N, and y = 2/3 x, a logical first guess would set x and y both equal to N^(1/3).

For N = 10^12, that means starting with x = y = 10,000. Then, Solver easily converges on the answers x = 11,447 and y = 7,631 (approx).

In my version of Excel, Solver will also find the correct solution starting with x and y as small as 10. But set them both to 1, and it will fail to find a solution. So a bit of trial and error might be required with your start values.

I’m kind of confused, how would you start with values of x = y =10,000, where would you put that on solver? Would it be the constrained values?

 

[MrFuz]

I’m kind of confused, how would you start with values of x = y =10,000, where would you put that on solver? Would it be the constrained values?

Are you able to send a xl2bb screenshot or the excel file So I could see what you done. Or say step by step what to do on solver.

 

[Fluff]

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[StephenCrump]

Are you able to send a xl2bb screenshot or the excel file So I could see what you done. Or say step by step what to do on solver.

Here's your workbook (attached to post #7), with 10 changed to 10^12

	A	B	C	D	E	F
1
2			VALUES	UNKNOWNS	EQN	CONSTRAINT
3	X^2*Y-10^12=0		X		-1E+12	0
4	3Y-2X=0		Y		0	0
5
Sheet1

Cell Formulas
Range	Formula
E3	E3	=(D3^2)*D4-10^12
E4	E4	=(3*D4)-(2*D3)

Named Ranges
Name	Refers To	Cells
solver_adj	=Sheet1!$D$3:$D$4	E3:E4

If I try start values in x (cell D3) and y (D4) both equal to 10,000, like this ...

		VALUES	UNKNOWNS	EQN	CONSTRAINT
X^2*Y-10^12=0		X	10000	0	0
3Y-2X=0		Y	10000	10000	0

... and run your version of Solver, I get the solution:

Book5.xlsx
	A	B	C	D	E	F
1
2			VALUES	UNKNOWNS	EQN	CONSTRAINT
3	X^2*Y-10^12=0		X	11447.1424	0	0
4	3Y-2X=0		Y	7631.42828	0	0
5
Sheet1

Cell Formulas
Range	Formula
E3	E3	=(D3^2)*D4-10^12
E4	E4	=(3*D4)-(2*D3)

Named Ranges
Name	Refers To	Cells
solver_adj	=Sheet1!$D$3:$D$4	E3:E4

Similar happens if I start with guesses of x=y=10, but the "solution" lacks some precision.

 

[MrFuz]

Here's your workbook (attached to post #7), with 10 changed to 10^12

	A	B	C	D	E	F
1
2			VALUES	UNKNOWNS	EQN	CONSTRAINT
3	X^2*Y-10^12=0		X		-1E+12	0
4	3Y-2X=0		Y		0	0
5
Sheet1

Cell Formulas
Range	Formula
E3	E3	=(D3^2)*D4-10^12
E4	E4	=(3*D4)-(2*D3)

Named Ranges
Name	Refers To	Cells
solver_adj	=Sheet1!$D$3:$D$4	E3:E4

If I try start values in x (cell D3) and y (D4) both equal to 10,000, like this ...

		VALUES	UNKNOWNS	EQN	CONSTRAINT
X^2*Y-10^12=0		X	10000	0	0
3Y-2X=0		Y	10000	10000	0

... and run your version of Solver, I get the solution:

Book5.xlsx
	A	B	C	D	E	F
1
2			VALUES	UNKNOWNS	EQN	CONSTRAINT
3	X^2*Y-10^12=0		X	11447.1424	0	0
4	3Y-2X=0		Y	7631.42828	0	0
5
Sheet1

Cell Formulas
Range	Formula
E3	E3	=(D3^2)*D4-10^12
E4	E4	=(3*D4)-(2*D3)

Named Ranges
Name	Refers To	Cells
solver_adj	=Sheet1!$D$3:$D$4	E3:E4

Similar happens if I start with guesses of x=y=10, but the "solution" lacks some precision.

thanks so much!!!