# Rewriting function equation

• Apr 8th 2007, 12:03 PM
Patience
Rewriting function equation
Rewrite the equation y = –2x – 4 as a function of x.

Please rtell me this is right.....

y + 4 = -2x
• Apr 8th 2007, 12:08 PM
Jhevon
Quote:

Originally Posted by Patience
Rewrite the equation y = –2x – 4 as a function of x.

Please rtell me this is right.....

y + 4 = -2x

not completely. a function of x means we want x ONLY on one side of the equal sign.

so

y = –2x – 4
=> -2x = y + 4 ..........you were right up to here
=> x = (y + 4)/-2 ......divide both sides by -2
=> x = (-1/2)y - 2
• Apr 8th 2007, 12:13 PM
CaptainBlack
Quote:

Originally Posted by Patience
Rewrite the equation y = –2x – 4 as a function of x.

Please rtell me this is right.....

y + 4 = -2x

Writing this as a function of x would usually require something like:

y=f(x),

where f:x in R -> -2x -4

or alternatively y(x)=-2x -4.

RonL
• Apr 8th 2007, 12:32 PM
Jhevon
Quote:

Originally Posted by CaptainBlack
Writing this as a function of x would usually require something like:

y=f(x),

where f:x in R -> -2x -4

or alternatively y(x)=-2x -4.

RonL

well that's true, but i just figure she made a typo or phrased the question incorrectly.

afterall, what self-respecting math book would give a problem where the solution is just to add (x) on one side? seems trivial to me
• Apr 8th 2007, 11:04 PM
CaptainBlack
Quote:

Originally Posted by Jhevon
well that's true, but i just figure she made a typo or phrased the question incorrectly.

afterall, what self-respecting math book would give a problem where the solution is just to add (x) on one side? seems trivial to me

Yes, but I can't let misuse of mathematical language go without comment.

intended it is of some importance to show that the question as asked
means something entirely different.

RonL
• Apr 8th 2007, 11:16 PM
Jhevon
Quote:

Originally Posted by CaptainBlack
Yes, but I can't let misuse of mathematical language go without comment.