Question

How do you solve `0=10x^2 + 9x-1` using the quadratic formula?

Answer 1

I will show you how and let you do the calculations

Explanation:

First you need to know the standard form which is:

`y=ax^2+bx+c`

In your case set:

`y=0` This is the condition needed any way to find where the graph crosses the x-axis.

`a=10`

`b=9`

`c=(-1)` the negative or minus is very important

These are then substituted into:

`x = ( b +- sqrt( b^2 - 4ac))/(2a)`

If the curve crosses the line in two places you will have two answers. If it is such that the x-axis is tangential to the curve then you only have one solution. If the curve is such that it does not cross the x-axis then (I think!) `b^2 - 4ac` is negative. You will need to check it!!

In your case you will have:

`(9 +- sqrt( 9^2 - (4)(10)(-1)))/(2 times 10)`

Notice that I use brackets to make sure that the positive or negative state of the values can be included. Reduces confusion!!!

Now you have a go at doing the calculation!!!