[MathMomma]

help!

I need to solve 2x^2-x-1=0

[Nathany]

You can use the quadratic formula. This formula can factor any trinomial. It is as follows:

[CENTER]-b+or-sqrt(b^2-4ac)
2a =x

The reason there is a plus or minus is because there are usually 2 answers to a trinomial.

a is the number the squared variable is multiplied by, in this case 2. (2x^2)
b is the number the variable is multiplied by, in this case -1. (-x)
c is the number the number with no variable is, in this case -1. (-1)

Now, all you have to do is find the answers to the equation:

1+or-sqrt[(-1)^2-4(2)(-1)]
2a =x

Sorry if you already know what the quadratic formula is but I can only assume that it is completely new to you.

[Nathany]

Sorry, the underlined part is supposed to be all divided by the 2a and that quotient will be x.

Also, In the second equation 2a should be 2(2).

[Unknown008]

Well, it's a perfect square... by inspection, we know that:



I don't find any serious need to use the quadratic formula, which is more time consuming... and if it's difficult to understand the formula, let me post it:

For a quadratic equation of the form:



The formula for solving x is: