Consider this:

A rectangle is 3 cm longer than it is wide. It has an area of 40 cm^2.

So, let the width be x => the length is x + 3 => the area is x(x + 3)

So answers may appear than are not solutions (unless you want to make a new topic in maths with 'negative lengths' )

Bob

]]>Kaboobly doo with the restrictions.

]]>The solution has no flaws except that you didn't set any restrictions.

]]>1) Why must it be easy to plug in? Does that invalidate the solution?

2) There are some obvious faults with the whole idea and I only presented it when I was sure the OP had already been satisfied.

]]>That is based on the simplicity of the solution. If it was something worse, you wouldn't be able to substitute and check easily without a computer.

]]>It arises because of the method of solution.

Bob

]]>But I think you should explain why -2 isn't a solution.

Spurious solutions are detected by plugging in. -2 does not work.

]]>Nice one. But I think you should explain why -2 isn't a solution.

]]>]]>

and

I realise it will be hard for you to believe it but, sometimes, even teachers talk a load of rubbish.

aude sapere

Bob

]]>Of course he said. But I forgot. I think it is so that we make sure neither side is negative.

Hi 295Ja

You're welcome. Hope everything else was okay during the storm.

]]>An average of 20 storms and/or typhoons per year enters the Philippines usually from July through October.

By the way, I'm now moving on to solving problems about inequalities then 2 dimensional coordinate system.

Glad I could ask problems I can't solve here!