Find the gradient of the curve y=2x^3 - 5x^2 + 46x + 87 at the point where it crosses the x axis.

I'm having real problems with this one as all the examples i've done before have given me a full set of co-ordinates.

I know that it will cross the x axis when y equals 0 so i have at least one co-ordinate. I differentiated it to 6x^2 - 10x + 46 I then thought about making 6x^2 - 10x = -46 and trying to get a value of x from that but i'm getting nowhere.

Any help on this is apprecciated