pls help

[minor bear]

I just want to know why they have used 3y-x = 0 and not y -x = 0. Is there a rule that I'm not taking into account or?

Thank you

[craggy wolf]

y-x=0 will give you when the gradient is 0 but ur after when the gradient is infinite so dx/dy=0

or in other words the denominator of dy/dx=0

[minor bear]

ahhh gotcha. but why do i need the gradient to be infinite?

[deep hemlock]

gradient of a vertical line is infinite/undefined
gradient is difference in y/ difference in x
when a line is vertical the difference in x is 0.
at p and q the graident is undefined because the tangents at those points are vertical

[minor bear]

thank you both 👍