Shouldnt the answer be zero? (1 Viewer)

[jane1820]

this is the worked solution For mastering mathematics year 11 advanced chapter 7B, problem 2.b

anyways if the lim is h approaches zero, shouldnt u sub in h as zero (numerator) and hence the whole thing is zero?

if u wanted to solve it from the beginning it is:
Define the function f(x) = 1/x
a. Show that f(x+h) - f(x) = (-h)/(x(x+h))
b. Hence, differentiate y=1/x using first principle, and show that f’(x) = -1/x^2

 

[cheesynooby]

I think they just did it wrong
the formula is lim [f(x + h) - f(x)]/h, not just f(x + h) - f(x)
which turns out a limit of -1/x(x+h)
(but yes the limit to the thing above is 0)

 

[jane1820]

I think they just did it wrong
the formula is lim [f(x + h) - f(x)]/h, not just f(x + h) - f(x)
which turns out a limit of -1/x(x+h)
(but yes the limit to the thing above is 0)

its one of the stupid challenge mastering questions where they try to make everything make sense so they eliminate half of the equation and work step by step
so they got rid of the lim and added it later for some reason

i just wanted to check that the answer equals zero bc h=0 ---> answer is zero