Answer:
assuming you know about straight lines...
equation of the line :
[tex](y - 7) = \frac{7 - 2}{0 - ( - 1)} (x - 0)[/tex]
y=5x+7
a) let's take 0 and 1, (which is already given)
f(1)-f(0)
=>[ 5(1)+7]-[5(0)+7)]
=5
b) 2 and 0,
[5(2)+7]-[5(0)+7]
=10
ratio= 10/5=2
since the function is linear, i.e. the slope is constant, the difference in two values in successive in intervals depends only on the ratio of the size of interval
let's say we have intervals of size a and b
(as you can see the constant gets cancelled)
difference in outputs will be 5a and 5b respectively.
and hence, ratio will be a/b
hope this explains