Please help me this is timed!!
1 answer:
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Answer:
Part 1) The amount invested at 4% was $2,000
Part 2) The amount invested at 9% was $3,000
Step-by-step explanation:
we know that
The simple interest formula is equal to
where
I is the Final Interest Value
P is the Principal amount of money to be invested
r is the rate of interest
t is Number of Time Periods
Let
x------> the amount invested at 4%
5,000-x ----> the amount invested at 9%
in this problem we have
substitute in the formula above
so
therefore
The amount invested at 4% was $2,000
The amount invested at 9% was $3,000
is decreasing on some interval
if
for all
. Similarly,
is increasing on
if
for all
.
On the domain , we have
as the only critical point. So we need to check the sign of on two intervals,
and
.
On , pick any test value. Suppose we take
. Then
, so
is decreasing on this interval.
On , you'd find that
, so
is increasing on this interval.