If the simple interest on $6000 for 9 years is $2160, then what is the interest rate?
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Answer:
1. Behavior
The g(x) is large and positive when x is large and positive;
The g(x) is large and negative when x is large and negative.
2. y-intercept= -18
3. The zeros are: -3, -2 and 3
Step-by-step explanation:
1. End behavior:
To find this you have to know the leading coefficient of the variable with the highest degree, and whether the degree is even or odd.
(x + 3) = x positive, coefficient 1
(x + 2) = x positive, coefficient 1
(x − 3)= x positive, coefficient 1
The coefficient is 1*1*1= 1 = positive
There are 3 x, so it will be x^3= odd
The behavior for odd and positive will be:
g(x) is + ∞ when x=>+∞
g(x) is -∞ when x=>-∞
or
The g(x) is large and positive when x is large and positive;
The g(x) is large and negative when x is large and negative.
2. Y-intercept
The y-intercept is the value of y when the graph touches the y-axis. The y-axis is located at x=0, so to find the y-intercept you need to put x=0 on the graph function. Some graphs can have two y-intercepts but the graph on the question only has one. The calculation will be:
y-intercept = g(0)= (0+3)(0+2)(0-3)
y-intercept = 3*2*-3
y-intercept= -18
3. Zeros
The zeros mean the value of x that will result as g(x) as zero. At this coordinate, the graph will touch the x-axis since g(0) is located on the x-axis. That is why this coordinate also called an x-intercept. The function is expressed as the product of three things. If any of them is 0, then the result will be 0. So we have 3 zeros
+3=0
=-3
+2=0
=-2
-3=0
=3
The zeros are: -3, -2 and 3
Your calculator's cubic regression function can tell you the equation is
... f(x) = 2x³ + 5x² -12x = x(x +4)(2x-3)
The x-intercepts are -4, 0, +1.5.
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If you want to solve this "by hand", you can first of all recognize that since there is an x-intercept at 0, the cubic will only have three coefficients. That is, you can write the equation as
... f(x) = ax³ + bx² + cx
Substituting the given points (except (0, 0)) gives three linear equations in a, b, c.
... -a +b -c = 15 . . . . . for x=-1
... a + b + c = -5 . . . . for x=1
... 8a +4b +2c = 12 . . for x=2
adding the first two equations gives 2b=10, or b=5. Now, you can reduce the system to
... a + c = -10
... 4a +c = -4
Subtracting the first of these equations from the second gives 3a=6, or a=2. That tells you c=-12 (from a+c=10).
Then your equation is
... f(x) = x(2x² +5x -12)
Factoring by any of the usual techniques, or graphing, or using the quadratic formula will tell you the zeros (x-intercepts) are as above.
_____
Since the input values are sequential, you can also develop the function from differences of the output values. Those are 15, 0, -5, 12. First differences are -15, -5, +17. Second differences are +10, +22. The third difference is 12. Using the first of these differences in appropriate places in the interpolating polynomial formula, we have
... f(x) = 15 + (x+1)(-15 + (x)/2·(10 + (x-1)/3·(12))) = 2x³ +5x² -12x . . . . as above
