To calculate the equation of the tangent lines you need a) the coordinates of the tangent point and b) the gradient of the graph of the function at the tangent point.
. Thus the tangent point is and
To calculate the gradient (=first derivative) I rearrange the term of the function to:
. Use chain rule!
Therefore the slope of the tangent line is or
Use the coordinates of the tangent point and the value of the slope to calculate the equation of the tangentline.
Calculate the intersection between these 2 lines and you'll get
Two graphs f and g are symmetric to the y-axis if their equations satisfy the condition
for every x. You can easily show that the equation follows from if you change the x into (-x).
I can't help you to solve y - ył = 1
Maybe you have to use Newton-Raphson method to get an approximate value for y.