calculus
posted by lori .
use implicit differentiation to find an equation of the tangent line to the curve at the given point.
9x^2+xy+9y^2=19, (1,1) (ellipse)

18x + y + xy' + 18yy' = 0
y' = (18x+y)/(x+18y)
at (1,1) y' = 1
so, the line is
y1 = (x1)