You must know the quadratic formula to the point when somebody wakes you
at 3:00 am and says "What is the quadratic formula?", you must be able to
recite it , and go back to sleep in 20 seconds.
x^2+9x+20=0
x = (-9 ± √(81-4(1)(20))/2
= (-9 ± √1)/2
= ....
Hey, that factored! How do I know that?
x^2+9x+20=0
Solve using quadratic formula
1 answer