so 21 - 13, the money will be invested for 8 years.

OK...... your answer would be
- 10y^2 - 26y + 1/y
H0P3 It H3LPS :)
The height of the trapezoid is 2 cm
NOOOOO! Integers are whole numbers, so there are none between 0 and 1. Now, whether or not there are any numbers at all between 0 and 1 is a whole different story... :)