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williamwood1-Visitor
1-Visitor
September 17, 2011
Question

Really silly question from newbie :)

  • September 17, 2011
  • 3 replies
  • 2784 views

Hi, been using mathcad for my uni work, got a new assignment to do and just trying to enter a really simple equation and I can't see why its not working.

I'm typing f(x):=9x(4-3x)

But its complaining that this value must be a function but has the form: Unitless. I've done this before on other assignments but can't see why its not working.

The equation I really want to do is a little more complex but not much. Whats weird is I can enter f(x):=9x(4-3) and it doesn't complain. As soon as i enter an x inside the bracket it doesn't like it. The full equation is in the form f(x):= (5x(2+3x)(10-2x))/4(5+x)^7

I just want to plot this and realise i'll need some variable for x but it I can't even define the function.

Am I missing something really simple here.

Any help would be greatly appreciated.

Regards

Will

3 replies

F
FDS13-Aquamarine
13-Aquamarine
September 18, 2011

William,

Maybe some typing error. It seems to work fine in MC 15 M010

Filip

R
RichardJ19-Tanzanite
19-Tanzanite
September 18, 2011

If you want multiplication you should explicitly type it. Yes, Mathcad will insert implied multiplication, but only when there is no other possible meaning. If I type 9x(4-3x) What I get is 9*x(4-3*x), NOT 9*x*(4-3*x). So you have x as both a function (an undefined one): x(), and as a variable. Hence the error message.

M
MikeArmstrong1-Visitor
1-Visitor
September 19, 2011

It's never a silly question if you don't know the answer.

Mike

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