show that there are two tangents to the curve y=(1/5)x^5 - 10x that have a slope of 6.

So what I did so far is found the derivative of the function which is:

y'=x^4-10

Now.. I have the slope in general, but I need to show that there are two tangents with the slope of 6.

If I did this.. I am just guessing but:

6=x^4-10

solve for x and I get x=2 or x=-2 But Still not sure on this..

Can someone verify/correct me and continue on to finish this? Thanks in advance.