Write an algebraic expression for 8 less than 4 times a number

Crystal bought new art supplies that were on sale for $25.45. If

Keith_Richards [23]

Answer:

The orginal price was $33.09.

Step-by-step explanation:

You take 30% and move the decimal two places to the left, which gives you .3

Then mutiply .3 to $25.45. This gives you $7.64.

Add $7.64 to discounted price ($25.45) and you get $33.09.

5 0

3 years ago

1. A retirement account is opened with an initial deposit of $8,500 and earns 8.12% interest compounded monthly. What will the a

Rudik [331]

Answer:

Part A) $\$42,888.48$

Part B) $A=\$22,304$

Part C) The graph in the attached figure

Step-by-step explanation:

Part A) What will the account be worth in 20 years?

we know that

The compound interest formula is equal to

$A=P(1+\frac{r}{n})^{nt}$

where

A is the Final Investment Value

P is the Principal amount of money to be invested

r is the rate of interest in decimal

t is Number of Time Periods

n is the number of times interest is compounded per year

in this problem we have

$t=20\ years\\ P=\$8,500\\ r=0.0812\\n=12$

substitute in the formula above

$A=8,500(1+\frac{0.0812}{12})^{12*20}$

$A=8,500(1.0068)^{240}$

$A=\$42,888.48$

Part B) What if the deposit were compounded monthly with simple interest?

we know that

The simple interest formula is equal to

$A=P(1+rt)$

where

A is the Final Investment Value

P is the Principal amount of money to be invested

r is the rate of interest

t is Number of Time Periods

in this problem we have

$t=20\ years\\ P=\$8,500\\r=0.0812$

substitute in the formula above

$A=8,500(1+0.0812*20)$

$A=\$22,304$

Part C) Could you see the situation in a graph? From what point one is better than the other?

Convert the equations in function notation

$A(t)=8,500(1.0068)^{12t}$ ------> equation A

$A(t)=8,500(1+0.0812t)$ -----> equation B

using a graphing tool

see the attached figure

Observing the graph, from the second year approximately the monthly compound interest is better than the simple interest.

5 0

3 years ago

Consider the equation below. (If an answer does not exist, enter DNE.) f(x) = x4 ln(x) (a) Find the interval on which f is incre

Ainat [17]

Answer: (a) Interval where f is increasing: (0.78,+∞);

Interval where f is decreasing: (0,0.78);

(b) Local minimum: (0.78, - 0.09)

(c) Inflection point: (0.56,-0.06)

Interval concave up: (0.56,+∞)

Interval concave down: (0,0.56)

Step-by-step explanation:

(a) To determine the interval where function f is increasing or decreasing, first derive the function:

f'(x) = $\frac{d}{dx}$ [ $x^{4}ln(x)$ ]

Using the product rule of derivative, which is: [u(x).v(x)]' = u'(x)v(x) + u(x).v'(x),

you have:

f'(x) = $4x^{3}ln(x) + x_{4}.\frac{1}{x}$

f'(x) = $4x^{3}ln(x) + x^{3}$

f'(x) = $x^{3}[4ln(x) + 1]$

Now, find the critical points: f'(x) = 0

$x^{3}[4ln(x) + 1]$ = 0

$x^{3} = 0$

x = 0

and

$4ln(x) + 1 = 0$

$ln(x) = \frac{-1}{4}$

x = $e^{\frac{-1}{4} }$

x = 0.78

To determine the interval where f(x) is positive (increasing) or negative (decreasing), evaluate the function at each interval:

interval x-value f'(x) result

0<x<0.78 0.5 f'(0.5) = -0.22 decreasing

x>0.78 1 f'(1) = 1 increasing

With the table, it can be concluded that in the interval (0,0.78) the function is decreasing while in the interval (0.78, +∞), f is increasing.

Note: As it is a natural logarithm function, there are no negative x-values.

(b) A extremum point (maximum or minimum) is found where f is defined and f' changes signs. In this case:

Between 0 and 0.78, the function decreases and at point and it is defined at point 0.78;
After 0.78, it increase (has a change of sign) and f is also defined;

Then, x=0.78 is a point of minimum and its y-value is:

f(x) = $x^{4}ln(x)$

f(0.78) = $0.78^{4}ln(0.78)$