An=Asub1(r)n-¹
=5(-2)7-¹
=5(64)
A7=320
It looks like selections A and C are identical. (Neither is equivalent to 9^x.)
If B is supposed to be 3^(2x), it is equivalent to F and D and to the given expression.
Of course, D evaluates to 9^x, so is equivalent.
Choice E evaluates to 3^(x+2), which is not equivalent to 3^(2x).
The applicable choices appear to be
... B. 3^(2x)
... D. (3*3)^x
... F. (3^x)*(3^x)
We need to call for x minute
+ Phone Company A charges a monthly fee of $42.50, and $0.02 for each minute talk time. So we have to spend: <span>$42.50+ $0.02x
+ </span>Phone company B charges a monthly fee of $25.00, and $0.09 for each minute of talk time. So we have to spend: <span>$25.00+ $0.09x
We solve for x: </span>$42.50+ $0.02x> <span>$25.00+ $0.09x
or </span>$42.50- $25.00 > $0.09x- <span>$0.02x
and we have $0.07x<$27.50
or x< 27.50:0.07 and x< 393.86
The answer is:
If we have to call much time, at least 394 minutes, we should choose A
If not, choose B</span>
The total cost would be 200
