What have you tried so far?
The tangent is simply the value of the derivative at x=1. So first you have to know if the function y=-2x^5+7 is derivable at x=1 . If it is it should yield the value of the tangent.
So it should be something like the tangent at a point let's say x0 is simply f'(x0).
No, that is incorrect. The tangent is the LINE that touches the original curve at the point specified. The derivative merely gives the GRADIENT of the tangent. So more work will be required to get the tangent once the gradient has been found.
Now the OP can show some effort before we give any more guidance.