That is an expression and not an equation. Technically there is no answer. If however you meant to find when it is equal to zero, or to factor it then:
You probably will need to complete the square as this equation has no easy integer factors...
3x^2+4x-17=0 get the constant on the other side by adding 17 to both sides.
3x^2+4x=17 divide the whole equation by 3 so that the leading coefficient is equal to one...
x^2+4x/3=17/3, now halve the linear coefficient, (4/3)/2=2/3, square it (2/3)^2=4/9, and add that value to both sides...
x^2+4x/3+4/9=(4+51)/9 now the left side is a perfect square...
(x+2/3)^2=55/9 now take the square root of both sides...
x+2/3=±√(55/9) now subtract 2/3 from both sides...
x=-2/3±√(55/9) so there are two solutions...
x=(-2±√55)/3