formula is 
where A=final amount
P=principal
r=interest rate in decimal
n=number of times per year it is compounded
t=time in years
we want to find where
A=2P
and P=5745
and r=6.5%=0.065
n=monthly=12
remember that 
also that 
, solving for t
divide both sides by 5745 to simplify things a bit
I'd rather not simplify this because it give us a decimals and those aren't exact, if we combine, we get 12.065/12 for inside parenthases
take ln of both sides
divide both sides by 
using our calculator, t≈10.6927
so rounded, we get 10.7 years
<em>x</em> ^2 + <em>y</em> ^2 = 9 => <em>y</em> = <em>y(x)</em> = ± √(9 - <em>x</em> ^2)
Each cross section would be a square with side length equal to the vertical distance between the upper and lower semicircles defined by <em>y(x)</em>, which is
√(9 - <em>x</em> ^2) - (- √(9 - <em>x</em> ^2)) = 2 √(9 - <em>x</em> ^2)
The area of each square section is the square of this length,
(2 √(9 - <em>x</em> ^2)) = 4 (9 - <em>x</em> ^2) = 36 - 4<em>x</em> ^2
We get the whole solid for -3 ≤ <em>x</em> ≤ 3, so integrating gives a volume of
if it is solution point (4, –2) must satisfy both equations
(1) –3x – 2y = –8-->-3*4-2*(-2)=-8
-12+4=-8 then-->-8=-8 ok
(2) y = 2x – 5
-2=2*4-5=3---------->-2 is not 3
the point (4, –2) is not solution of the system of equations
