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Answer:
The equation contains exact roots at x = -4 and x = -1.
See attached image for the graph.
Step-by-step explanation:
We start by noticing that the expression on the left of the equal sign is a quadratic with leading term , which means that its graph shows branches going up. Therefore:
1) if its vertex is ON the x axis, there would be one solution (root) to the equation.
2) if its vertex is below the x-axis, it is forced to cross it at two locations, giving then two real solutions (roots) to the equation.
3) if its vertex is above the x-axis, it will not have real solutions (roots) but only non-real ones.
So we proceed to examine the vertex's location, which is also a great way to decide on which set of points to use in order to plot its graph efficiently:
We recall that the x-position of the vertex for a quadratic function of the form is given by the expression:
Since in our case and
, we get that the x-position of the vertex is:
Now we can find the y-value of the vertex by evaluating this quadratic expression for x = -5/2:
This is a negative value, which points us to the case in which there must be two real solutions to the equation (two x-axis crossings of the parabola's branches).
We can now continue plotting different parabola's points, by selecting x-values to the right and to the left of the . Like for example x = -2 and x = -1 (moving towards the right) , and x = -3 and x = -4 (moving towards the left.
When evaluating the function at these points, we notice that two of them render zero (which indicates they are the actual roots of the equation):
The actual graph we can complete with this info is shown in the image attached, where the actual roots (x-axis crossings) are pictured in red.
Then, the two roots are: x = -1 and x = -4.
<span>The correct answer is $1452.50 per year.
Explanation:<span>
We use the formula
</span></span>![P(1+\frac{r}{n})^{nt}+PMT(\frac{[(1+\frac{r}{n})^{nt}-1]}{\frac{r}{n}})\times (1+\frac{r}{n})](https://tex.z-dn.net/?f=P%281%2B%5Cfrac%7Br%7D%7Bn%7D%29%5E%7Bnt%7D%2BPMT%28%5Cfrac%7B%5B%281%2B%5Cfrac%7Br%7D%7Bn%7D%29%5E%7Bnt%7D-1%5D%7D%7B%5Cfrac%7Br%7D%7Bn%7D%7D%29%5Ctimes%20%281%2B%5Cfrac%7Br%7D%7Bn%7D%29)
,<span><span>
where P is the amount of principal invested, r is the interest rate as a decimal number, n is the number of times per year the interest is compounded, PMT is the monthly deposit added, and t is the number of years.
Since the amount of principal is not stated, we will assume that Bob is depositing the same amount every following year as he does the first year, so we will let PMT=P.
Our interest rate, r, is 4.2%; 4.2%=4.2/100=0.042.
The number of times the interest is compounded annually, n, is 1.
The amount of time, t, is 7.
We know he wants $50,000. This gives us the equation
50000=P(1+0.042/1)</span></span>⁽¹ˣ⁷⁾<span><span>+P{[(1+0.042/1)</span></span>⁽¹ˣ⁷⁾<span><span>]/(0.042/1)}*(1+0.042/1).
Simplifying this a bit, we have
50000=P(1.042)</span></span>⁷<span><span>+P((1.042</span></span>⁷<span><span>)/0.042)*(1.042).
We can factor out P, giving us
50000=P[1.042</span></span>⁷<span><span>+((1.042</span></span>⁷<span><span>)/0.042)*1.042].
This then gives us
50000=P(34.4234).
Divide both sides:
50000/34.4234 = (P(34.4234))/34.4234,
which gives us P=1452.50.</span></span>
Explanation:<span>
We use the formula
</span></span>
where P is the amount of principal invested, r is the interest rate as a decimal number, n is the number of times per year the interest is compounded, PMT is the monthly deposit added, and t is the number of years.
Since the amount of principal is not stated, we will assume that Bob is depositing the same amount every following year as he does the first year, so we will let PMT=P.
Our interest rate, r, is 4.2%; 4.2%=4.2/100=0.042.
The number of times the interest is compounded annually, n, is 1.
The amount of time, t, is 7.
We know he wants $50,000. This gives us the equation
50000=P(1+0.042/1)</span></span>⁽¹ˣ⁷⁾<span><span>+P{[(1+0.042/1)</span></span>⁽¹ˣ⁷⁾<span><span>]/(0.042/1)}*(1+0.042/1).
Simplifying this a bit, we have
50000=P(1.042)</span></span>⁷<span><span>+P((1.042</span></span>⁷<span><span>)/0.042)*(1.042).
We can factor out P, giving us
50000=P[1.042</span></span>⁷<span><span>+((1.042</span></span>⁷<span><span>)/0.042)*1.042].
This then gives us
50000=P(34.4234).
Divide both sides:
50000/34.4234 = (P(34.4234))/34.4234,
which gives us P=1452.50.</span></span>