F(x)=125-(125*0.2x)
to find the value of the phone after 3 years, you put x=3.
f(3)=125-(125*0.2(3))
f(3)=50
You first have to find the slope using the slope formula. That looks like this with our values:
. So the slope is -1/8. Use one of the points to first write the equation in y = mx + b form. We have an x and a y to use from one of the points and we also have the slope we just found. Filling in accordingly to solve for b gives us
and
. Adding 5/8 to both sides and getting a common denominator gives us that
. Writing our slope-intercept form we have
. Standard form for a line is Ax + By = C...no fractions allowed. So let's get rid of that 8 by multiplying each term by 8 to get 8y = -x - 11. Add x to both sides to get it into the correct form: x + 8y = -11
51 = 3 * 17, sum of 20, no good.
<span>52 = 2 * 2 * 13, sum of 17, no good. </span>
<span>54 = 2 * 3 * 3 *3, sum of 11. </span>
<span>The answer is 54. If you need more help, let me know.</span>
Simultaneous Equations
3x + y = 4
5x - y = 22
The signs of the matching values aren't the same so we add the rest of the equations.
8x = 26
Divide both sides by 8 to get x = 3.25
Now substitute back into the first equation.
(3 x 3.25) + y = 4
9.75 + y = 4
Subtract 9.75 from both sides
y = -5.75
Answer:
y = 18·8^x
Step-by-step explanation:
We assume you want a model that looks like y = ab^x.
To find the values of "a" and "b", you can fill in the given numbers and solve the system of equations:
18 = a·b^0
9216 = a·b^3
The first equation tells you ...
18 = a
Dividing the second equation by the first gives ...
9216/18 = (a·b^3)/(a·b^0) = b^3
512^(1/3) = b = 8
The exponential function is ...
y = 18·8^x
