Question 56786
3a^2 + 21a + 30 I will assume equals zero.
3a^2 + 21a + 30 = 0
3a^2 + 21a = -30
a^2 + 7a = -10
(a + 7/2)^2 = 49/4 - 40/4 = 9/4
a + 7/2 = +- 3/2
a = -7/2 +- 3/2
a = -5 or a = -2
{{{graph(300,300,-10,10,-10,10,3x^2+21x+30)}}}