Thread: Self-learner having trouble with quadratic equation

Hi. First of all - sincere apologies if this is in the wrong place. I have read the rules, but unfortunately don't really know all categories of mathematics, or what comes under which umbrella.

Anyway, simple quadratic equations I don't find difficult.

However, this problem is seriously getting to me. The exercise book I have bought claims the answer to be 0.2, but I simply cannot find out why. I thought QE were meant to have ± values, and this is just making me crazy.

(x-1)^2 = x(x-3)

I have expanded the brackets to find:

X^2-2x+1 = X^2-3x

But I have honestly no clue where to go from next. I have tried researching it, or finding other similar problems online but to no avail.

Thanks in advance.

This is a linear equation rather than quadratic. You have x^2 on both sides and it will cancel.

If you take x^2-3x from both sides you will get which simplifies to

It follows that is the solution because whereas gives



edit: as a background you can have one solution to a quadratic equation (technically 2 equal roots). This happens when the discriminant is equal to 0.

For example find the solution(s) to (answer in spoiler)

Spoiler:

Thanks very much. It's in the QE part of my workbook... and the answer is listed as 0.2. I had solved it as you did before, but just assumed that was too simple or something.

I'll assume it's a misprint - thanks for your help.

Originally Posted by S1919

(x-1)^2 = x(x-3)

Looks like that equation contains a typo: should be (x - 1)^2 = x(x + 3) ?
That would explain the .2 solution:
x^2 - 2x + 1 = x^2 + 3x
5x = 1
x = 1/5 = .2