x^2+6x-11=0

Question

x^2+6x-11=0

anonymous · Answer

x = (-6 +- sqrt(36-4*(-11))) / 2
x = (-6 +- sqrt(80))/2
x = -3 + 2*sqrt(5) or -3 - 2*sqrt(5)

strawberry17 · Answer

Do you know the quadratic formula? :)

strawberry17 · Answer

where $$x = \frac{ -b \pm \sqrt{b ^{2}- 4ac} }{ 2a }$$

strawberry17 · Answer

In this case, for the above problem, a=1,  b=6,  and c=-11.
You would plug the values of these into the quadratic formula.

anonymous · Answer

i would not use the formula, i would complete the square because $6$ is even

anonymous · Answer

$$x^2+6x-11=0\
x^2+6x=11\
(x+3)^2=11+9=20\x+3=\pm\sqrt{20}\x=-3\pm\sqrt{20}$$

anonymous · Answer

or if you prefer 
$$x=-3\pm2\sqrt{5}$$

strawberry17 · Answer

I guess you could do it both ways, because they both lead to the same solution. For me it was easier to just plug the values into the formula, but I got the same answer as you  :)

anonymous · Answer

yes of course
but because $6$ is even, i don't have to deal with a denominator when i complete the square
the quadratic formula forces a denominator on you, whether you need it or not

strawberry17 · Answer

yep you are right :)