Question 520997
Solve: 28+5a-12a^2=0
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First thing to do is rewrite the equation in decending order
-12a^2+5a+28=0
Get rid of a negative lead coefficient by multiplying both sides of equation by -1
12a^2-5a-28=0
This doesn't look very easy to factor, so consider using the quadratic formula to solve.
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
If you are good at factoring, the answers are: 
(3a+4)(4a-7)=0
a=-4/3
or
a=7/4