Whats the answer to this equation 3x²+4x-17

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