Anyone maths please?

[excelos]

hello!

I want to insert this equation to Excel:

I came up with this (obviously, P = I7 cell, etc)
=(I7*6*sqrt(J7)*(1.99-J7*(1-J7)*(2.145-3.93*J7+2.70*J7^2)))/(F7*sqrt(G7)*(1-2*J7)*(1-J7)^1.5)

What could be wrong in the above function?

Thanks!

 

[SteveO59L]

what happens when you try?

 

[excelos]

what happens when you try?

it calculates some weird things, eg negative numbers

 

[Jonmo1]

You probably need to consider the order of operations..

^ is calculated first
* and / are next
and +- are last

putting calcs in () will override that order, anything in () is done first.

Example
(F7*sqrt(G7)*(1-2*J7)*(1-J7)^1.5)
1-J7 will be done first, and the result of that will then be applied to ^1.5

If you intended the ^1.5 to be done last, 'after' all the multiplications, then you would do
((F7*sqrt(G7)*(1-2*J7)*(1-J7))^1.5)

That way, all of this is done first
F7*sqrt(G7)*(1-2*J7)*(1-J7)
Then that result is applied to ^1.5

 

[SteveO59L]

what values are in each of the referenced cells?

 

[excelos]

what values are in each of the referenced cells?

I7 = 85
J7 = 0.466667
F7 = 0.00997
G7 = 0.006[TABLE="width: 64"]
<tbody>[TR]
[TD="width: 64, align: right"][/TD]
[/TR]
</tbody>[/TABLE]

 

[Jonmo1]

ok, I get a result of 30686883 with those values.
What result are you expecting?

I'd suggest using the Formula evaluation tool on the Formulas tab, and watch the calculations happen 1 step at a time.
I'm failry sure the issue is with the order of calculations.

 

[excelos]

You probably need to consider the order of operations..

^ is calculated first
* and / are next
and +- are last

putting calcs in () will override that order, anything in () is done first.

Example
(F7*sqrt(G7)*(1-2*J7)*(1-J7)^1.5)
1-J7 will be done first, and the result of that will then be applied to ^1.5

If you intended the ^1.5 to be done last, 'after' all the multiplications, then you would do
((F7*sqrt(G7)*(1-2*J7)*(1-J7))^1.5)

That way, all of this is done first
F7*sqrt(G7)*(1-2*J7)*(1-J7)
Then that result is applied to ^1.5

I think I am happy to do the powers first, then the multiplications/divisions and last the additions/substractions.
I think that's what the correct maths imply, when we write an equation and that's what should be applied to the equation.

 

[SteveO59L]

BODMAS

Brackets
Others
Division
Multiplication
Addition
Subtraction

 

[Jonmo1]

The ^ was just an example...
Here's another possible issue

2.145-3.93*J7+2.70*J7^2

Using brackets to illustrate, this is the order that would be calculated
(2.145-(3.93*J7))+(2.70*(J7^2))

Is that the way you're expecting ?