Use the quadratic formula:
\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\)
x^2+5x+c=ax^2+bx+c
a=1
b=5
c=?
Plug it into the formula and we get
\(x = {-5 \pm \sqrt{5^2-4(1)c} \over 2(1)}\)
and solve to get
\(x = {-5 \pm \sqrt{25-4c} \over 2}\)
now, we know that everything is the same except for the discriminant(the stuff in the square root), and we also know that the disriminant is c
Set them equal to get
25-4c=c
Now solve to get
25=5c
and c=5
XD
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