Answer:
we have to learn this in middle school
Step-by-step explanation:
Answer:

Step-by-step explanation:
We are given that
Height of man=5 foot

Height of street light=20ft
We have to find the rate of change of the length of his shadow when he is 25 ft form the street light.
ABE and CDE are similar triangle because all right triangles are similar.







Hence, the rate of change of the length of his shadow when he is 25 ft from the street light=
Answer:
Step-by-step explanation:
Hello, please consider the following.

So this is divisible by 3.
Now, to prove that this is divisible by 9 = 3*3 we need to prove that
is divisible by 3. We will prove it by induction.
Step 1 - for n = 1
4+17=21= 3*7 this is true
Step 2 - we assume this is true for k so
is divisible by 3
and we check what happens for k+1

is divisible by 3 and
is divisible by 3, by induction hypothesis
So, the sum is divisible by 3.
Step 3 - Conclusion
We just prove that
is divisible by 3 for all positive integers n.
Thanks