Find the largest value of $x$ such that $3x^2 + 17x + 15 = 2x^2 + 21x + 12 - 5x^2 + 17x + 34.$
Simplify as
6x^2 - 21x - 31 = 0
x = [ 21 + sqrt [ 441 + 744 ] ] / 12 = [ 21 + sqrt (1185) ] / 12
+447 
