Find the tangent plane to f(x,y)=x2+y2f(x, y) = x^2 + y^2f(x,y)=x2+y2 at (1,2)(1, 2)(1,2).
z=2x+4y−5z = 2x + 4y - 5z=2x+4y−5
z=2x+4yz = 2x + 4yz=2x+4y
z=x+y−5z = x + y - 5z=x+y−5
z=2x+4y+5z = 2x + 4y + 5z=2x+4y+5