How do you solve -0.12x^2 + 1.4x - 3.5 = 0.5 using the quadratic formula?

1 Answer
Jul 9, 2015

I found:
x_1=5
x_2=20/3

Explanation:

Ok...I`ll try to "simplify" it a bit to avoid decimals...(I do not like them!).
I can write it as:
-12/100x^2+14/10x-35/10=5/10
getting rid of the denominators (after taking 100 as common) I got:
-12x^2+140x-400=0
that is in the form:
ax^2+bx+c=0
With:
a=-12
b=140
c=-400
I now use the Quadratic Formula:
x_(1,2)=(-b+-sqrt(b^2-4ac))/(2a)=(-140+-sqrt(140^2-4(-12*-400)))/(2*-12)=
=(-140+-sqrt(400))/-24=(-140+-20)/-24=
You get two solutions:
x_1=(-140+20)/-24=5
x_2=(-140-20)/-24=160/24=20/3