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

1 Answer
Oct 13, 2015

I will show you how and let you do the calculations


First you need to know the standard form which is:


In your case set:

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



#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!!!