Math Help now !!!! Plz
posted by David .
Solve using the quadratic formula
Learn the quadratic formula:
x = [-b +/-sqrt(b^2 -4ac)]/2a
In your case a = 1, b = -4 and c = -21
x = [4 +/-sqrt(100)]/2
You finish it. You surely know what the square root of 100 is.