Question 548232
{{{-2x^2=72}}}
Divide both sides by -2 to get:
{{{-2x^2/-2=72/-2}}}
{{{x^2=-36}}}
Take the square root of both sides to get:
{{{x=+sqrt(-36)}}}
or
{{{x=-sqrt(-36)}}}
Now we know that {{{sqrt(-1)=i}}} by definition
{{{x=+sqrt(-1*36)}}}
or 
{{{x=-sqrt(-1*36)}}}


{{{x=+sqrt(-1)*sqrt(36)}}}
or 
{{{x=-sqrt(-1)*sqrt(36)}}}

{{{x=+i*sqrt(36)}}}
or
{{{x=-i*sqrt(36)}}}

{{{x=+i*6}}}
or
{{{x=-i*6}}}
(Which is answer d)