Let fxy4x25xyy2 Then an implicit equation for the tangent pl

Let f(x,y)=4x2?5xy+y2. Then an implicit equation for the tangent plane to the graph of f at the point (?1,0) is

answer:4x²-5xy+y²+8x-5y+4=0
sorry i mistook it to linear co.ordiante geometry..
this wud be the crct answer..
f(-1,0)=4
equation for tangent is therfore..
f(x,y)-f(x1,y1)=f_x(x1,y1) (x-x1) + f_y(x1,y1) (y-y1)
4x²-5xy+y²-4 = -8(x+1) + 5(y)
4x²-5xy+y²+8x-5y+4=0 gives the equation to the pair of tangents to graph of f(x).