Expert: Sherry Wallin - 12/30/2010

Question
A=LW make (L)the subject.  P=2L+2B  make (L) the subject   xoverw plus 5 equals 7  make (x) the subject   A=TTr^2 make (R)the subject.   please

Answer
John~

Sorry but I haven't got a clue what you want. What is a subject? This isn't typical mathematical language. Also "xoverw plus 5 equals 7" is ambiguous because the way you have it spelled out is equivalent to x/w + 5 = 7, is this what you meant it to mean?

I suspect what you mean by "subject" is that you want to make the subject the variable. I will assume this is the case.

A = LW and you want to solve for L which means you want L by itself on one side of the equation.
So what operation is there with LW? Yes multiplication. What is the inverse (opposite) operation to multiplication? Yes division, so divide both sides by W to get L by itself: A/W = L

P=2l+2B and to solve for L:
P-2b = 2l
P/2 -2b/2 = 2l?2 -> P/2 - b = L

x/w + 5 = 7 to solve for x, first subtract 5 from each side
x/w = 2
now multiply both sides by w:
x = 2w

A = TTr^2 and you want R the variable, you have no R, you only have r: So A = TTr^2 divide both sides by TT getting A/TT = r^2 and now take the square root of both sides getting +-sqrt(A/TT) = r

Math Prof