24 and 28
These are the only two numbers (other than 20 itself) that have a factor of 4. And if you were to find all of their common factors, 4 would be the greatest!
Answer : 7,889
Hundreds digit : 800
Tens digit : 80
800 ÷ 80 = 10 (800, the hundreds digit, is 10 times as great as the tens digit, 80)
Substitute 1/x with u
dx = -x^2 du
-1/4 integral of e^u•du
Apply exponential rule -(e^u)/4
Undo the substitution u is 1/x
Answer is (-(e^1/x)/4 ) + C
