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Free Software Tool which solves a first order equation: ax + b = c

Updated on June 23, 2012

Free Software Tool which solves a first order equation:

ax+ b = c

This hub provides a program for math students working with a first order algebraic equation. The user is prompted for coefficients a, b and c, while the software solves for unknown x. You will need Microsoft Excel. We will go through how to install the program here. It will involve copying and pasting my code into Excel. Open up Excel, save the new file as “1st order.xlsm”. In newer versions of Windows, you will save as type “Excel Macro-Enabled Workbook”. The workbook/spreadsheet should contain three sheets: “Sheet1”, “Sheet2”, and ‘Sheet3”. Right click on the “Sheet3” tab at bottom, and delete it. Do the same for “Sheet2”. “Sheet1” remains. It will be a spreadsheet with embedded code to solve the equation. Our program will look for the name “Sheet1”, so do not change it. You will need access to the Developers tab in Excel. To make it visible in the new spreadsheet, do as follows:

1. File --> Options (click)

2. Customize Ribbon (click)

3. Check the “Developer” box and click “OK” at bottom.

4. You will now see “Developer” tab. Click it.

5. Section dealing with macros and VBA (Visual Basic) is now visible at far left.

We will create a macro, into which we will soon paste some code. Over on the left, find and click the tab “Record Macro”. A box pops up. It has been given a default name, such as “Macro1”. Just leave it as is. There will also be a shortcut key entry, make it “ctrl a”. Click OK. At this point, do not press any keys or perform random mouse clicks, or you will actually start recording keystrokes/commands in the macro. Rather, immediately click the “stop recording” tab, located in same place where “Record Macro” was. We have created a blank routine into which we will now place some code. Click on “Macros” tab and you will see the blank macro we just created. Click “Edit”. The macro will open up in a window, see picture in the diagram. Place the blinking cursor as shown, then copy and paste in this code:

On Error GoTo errorhandle

Dim ast As String, a As Single, bst As String, b As Single, cst As String, c As Single

Dim eqnstr As String, xdecimal As Single, xfractionstr As String, decsolnstr As String, num As Single

Dim lenast As Single, lenbst As Single, lencst As Single

Dim rtast As String, rtbst As String, rtcst As String

Dim lfast As String, lfbst As String, lfcst As String

Dim slasha As Single, slashb As Single, slashc As Single, endstr As String

Dim counta As Single, countb As Single, countc As Single, searchstr As String

Dim x As Single

ast = InputBox("enter coefficient 'a' for ax + b = c. Include sign if negative," _

& "do not use commas or spaces, fractions are OK: 5, -5, 2/15, -2/15....")

bst = InputBox("enter coefficient 'b' for ax + b = c. Include sign if negative," _

& "do not use commas or spaces, fractions are OK: 5, -5, 2/15, -2/15....")

cst = InputBox("enter coefficient 'c' for ax + b = c. Include sign if negative," _

& "do not use commas or spaces, fractions are OK: 5, -5, 2/15, -2/15....")

ast = Trim(ast)

bst = Trim(bst)

cst = Trim(cst)

lenast = Len(ast)

lenbst = Len(bst)

lencst = Len(cst)

If InStr(ast, "/") <> 0 Then

slasha = InStr(ast, "/")

lfast = Left(ast, (slasha - 1))

rtast = Right(ast, (lenast - slasha))

a = Val(lfast) / Val(rtast)

Else

a = Val(ast)

rtast = "1"

End If

If InStr(bst, "/") <> 0 Then

slashb = InStr(bst, "/")

lfbst = Left(bst, (slashb - 1))

rtbst = Right(bst, (lenbst - slashb))

b = Val(lfbst) / Val(rtbst)

Else

b = Val(bst)

rtbst = "1"

End If

If InStr(cst, "/") <> 0 Then

slashc = InStr(cst, "/")

lfcst = Left(cst, (slashc - 1))

rtcst = Right(cst, (lencst - slashc))

c = Val(lfcst) / Val(rtcst)

Else

c = Val(cst)

rtcst = "1"

End If

If b > 0 Then eqnstr = ast & "x + " & bst & " = " & cst

If b < 0 Then eqnstr = ast & "x " & bst & " = " & cst

If b = 0 Then eqnstr = ast & "x " & " = " & cst

num = c - b

xdecimal = num / a

decsolnstr = "x = " & xdecimal

a = a * Val(rtast) * Val(rtbst) * Val(rtcst)

b = b * Val(rtast) * Val(rtbst) * Val(rtcst)

c = c * Val(rtast) * Val(rtbst) * Val(rtcst)

x = 0

counta = 0

ast = Str(a)

Do

searchstr = Mid(ast, (Len(ast) - x), 1)

x = x + 1

If searchstr = "0" Then

counta = counta + 1

Else

Exit Do

End If

Loop

x = 0

countb = 0

bst = Str(b)

Do

searchstr = Mid(bst, (Len(bst) - x), 1)

x = x + 1

If searchstr = "0" Then

countb = countb + 1

Else

Exit Do

End If

Loop

If countb < counta Then counta = countb

x = 0

countc = 0

cst = Str(c)

Do

searchstr = Mid(cst, (Len(cst) - x), 1)

x = x + 1

If searchstr = "0" Then

countc = countc + 1

Else

Exit Do

End If

Loop

If countc < counta Then counta = countc

ast = Left(ast, Len(ast) - counta)

bst = Left(bst, Len(bst) - counta)

cst = Left(cst, Len(cst) - counta)

ast = Trim(ast)

bst = Trim(bst)

cst = Trim(cst)

a = Val(ast)

b = Val(bst)

c = Val(cst)

num = c - b

If (num < 0 And a < 0 Or num > 0 And a < 0) Then xfractionstr = "x = " & -num & "/" & -a

If (num < 0 And a > 0 Or num > 0 And a > 0) Then xfractionstr = "x = " & num & "/" & a

If (num = 0) Then xfractionstr = "0"

Sheets("Sheet1").Activate

Range("A1").Select

ActiveCell.Value = "equation"

Range("B1").Select

ActiveCell.Value = "decimal solution for 'x'"

Range("A2").Select

ActiveCell.Value = eqnstr

Range("B2").Select

ActiveCell.Value = decsolnstr

Range("C1").Select

ActiveCell.Value = "fractional solution for 'x'"

Range("C2").Select

ActiveCell.Value = xfractionstr

Range("C3").Select

ActiveCell.Value = "may need to simplify fraction"

Range("A1").Select

Range(Selection, "C3").Select

Selection.Columns.AutoFit

ActiveWindow.Zoom = True

With Selection

.HorizontalAlignment = xlCenter

.VerticalAlignment = xlBottom

.WrapText = False

.Orientation = 0

.AddIndent = False

.IndentLevel = 0

.ShrinkToFit = False

.ReadingOrder = xlContext

.MergeCells = False

End With

Range("C4").Select

Exit Sub

errorhandle:

MsgBox _

("There was an error. Most likely with coefficients you entered. Try again."), vbOKOnly


When you paste the code in, it is likely there will be two areas in red indicating errors in the transfer (one area near top of code, one at bottom). They can be corrected (see pictures) by placing the mouse cursor exactly flush with the “dash” at line end and hitting “delete key”. The red type will become black, indicating it is now correct.

Close the program box and re-save the Excel workbook, keeping it open. Hit “ctrl a” and the program will run. That’s it, hope it works well for you.

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