GCSE Maths Question

Etaqua · 7 Apr 2006 at 20:46

I'm stuck with finding equations from exponential graphs. I can do quadratics - no problem. But these just seem a lot harder.

There is an example of how to find quadratic equations from graphs in the CGP revision guide, but not exponentials. The "Acid Test" question asks you: "The graph shown here is thought to be represented by the equation Y = PQ^x where P and Q are unknown constants. Use the graph to find the values of P and Q".

Since you don't have a copy of the graph, I'll give you the two points I found on it: (0, 50) and (2, 100). In the method they say you need two points, preferably on either the X-axis or Y-axis, only one is.

Could someone give me a walkthrough of how to do it and questions like this?

TIA, Etaqua.

Etaqua · 7 Apr 2006 at 20:48

It's not homework, it's a page in the CGP revision guide.

Edit: I already have the answers, they're in the back of the book, but I don't know how to do this type of question.

Q = 1.41 and P = 50, if you need proof I'm not cheating on some homework.

Etaqua · 7 Apr 2006 at 20:52

Mmm, I don't think we do logs at GCSE stage, so I don't think that's how we're supposed to do it. There is no mention of them on the page which (doesn't) explains how to solve them.

Etaqua · 7 Apr 2006 at 21:31

Amleto, you are a lifesaver. You also reminded me that x^0 is not 0, but 1. I think that's where I went wrong...

Thanks @ Amleto.

*hands Amleto a beer and young woman*