Consider the graph plotted by the equation
where , , and is a constant.
Let be the gradient of the normal to a curve of the graph at the point where , is a real positive integer. Determine the value of
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Implicit differentiation of k x + y k + x x = x k + k y + y y gives ( k x ) ( ln k ) + ( k ) ( y k − 1 ) ( d x d y ) + ( x x ) ( ln x + 1 ) = ( k ) ( x k − 1 ) + ( k y ) ( ln k ) ( d x d y ) + ( y y ) ( ln y + 1 ) ( d x d y ) ( k ) ( y k − 1 ) ( d x d y ) − ( k y ) ( ln k ) ( d x d y ) − ( y y ) ( ln y + 1 ) ( d x d y ) = ( k ) ( x k − 1 ) − ( k x ) ( ln k ) − ( x x ) ( ln x + 1 ) ( d x d y ) ( ( k ) ( y k − 1 ) − ( k y ) ( ln k ) − ( y y ) ( ln y + 1 ) ) = ( k ) ( x k − 1 ) − ( k x ) ( ln k ) − ( x x ) ( ln x + 1 ) d x d y = ( k ) ( y k − 1 ) − ( k y ) ( ln k ) − ( y y ) ( ln y + 1 ) ( k ) ( x k − 1 ) − ( k x ) ( ln k ) − ( x x ) ( ln x + 1 ) For constant k , at every point ( t , t ) where t ∈ Z + , t ≥ k , d x d y = 1 , hence G k , t = − 1 . Therefore k = 2 ∏ 2 0 1 6 ( t = k ∏ k + 2 0 1 5 G k , t ) = 1