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

1 Answer
Tony B
Oct 13, 2015

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!!!

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