Find an equation of the tangent like at x= a

Question

Y=x^2/4 ; a= -4

I’m not sure how to find it with only y and not a point of a graph the use y-y1=m(x-x1)

Answer 1

dy/dx=x/2

At x=-4 the slope of the tangent is -2

The tangent must pass thru (-4,4)

Therefore the tangent line is -2 = (y-4)/(x+4) which can be "massaged" into any form you need.