Domain and range of the function \(y=\frac{1}{x}\)
Now, let's figure out the domain first. The domain of a function just means the possible range of x-values that output a real y-value.
Let's consider that. Is there any number for x that would output a nonreal y-value?
Yes, 0. If you plug in 0 for x, you get a nonreal y-value. Will any others? No. I've made a table of the first few domain options.
| Possible Domain | Corresponding y-value | Is it real? |
| -5 | \(\frac{1}{-5}\) | Yes |
| -4 | \(\frac{1}{-4}\) | Yes |
| -3 | \(\frac{1}{-3}\) | Yes |
| -2 | \(\frac{1}{-2}\) | Yes |
| -1 | \(\frac{1}{-1}\) | Yes |
| 0 | \(\frac{1}{0}\) | No, a number divided by 0 is undefined. |
| 1 | \(\frac{1}{1}\) | Yes |
| 2 | \(\frac{1}{2}\) | Yes |
| 3 | \(\frac{1}{3}\) | Yes |
| 4 | \(\frac{1}{4}\) | Yes |
| 5 | \(\frac{1}{5}\) | Yes |
You can see that any numer, except 0, will output a real y-value. Therefore, the domain is any number that isn't 0.
Domain: \(\{x\in {\rm I\!R}\hspace{1mm}: x\neq0\}\)
In other words, the domain is apart of the real numbers except 0.
Let's think about the range, too. The range is set of all possible values that the function can actually produce. Let's try making a table for that:
| Possible Range | Corresponding x-value | Is it real? |
| -3 | \(-\frac{1}{3}\) | Yes |
| -2 | \(-\frac{1}{2}\) | Yes |
| -1 | \(-1\) | Yes |
| 0 | No solution | No |
| 1 | \(1\) | Yes |
| 2 | \(\frac{1}{2}\) | Yes |
| 3 | \(\frac{1}{3}\) | Yes |
You might be wondering why 0 has "no solution" on it. Well, let's try and solve it:
| \(y=\frac{1}{x}\) | Substitute in 0 for y. |
| \(0=\frac{1}{x}\) | Multiply my x on both sides. |
| \(0=1\) | This is a nonsensical answer. Since \(0\neq1\), there is no solution. Therefore, 0 cannot be a possible range value. |
Any other real number works, so our range is:
\(\{f(x)\in {\rm I\!R}\hspace{1mm}:f(x)\neq0\}\)
To recap, the domain and range is as follows
Domain: \(\{x\in {\rm I\!R}\hspace{1mm}: x\neq0\}\)
Range: \(\{f(x)\in {\rm I\!R}\hspace{1mm}:f(x)\neq0\}\)
To answer your second question about what does \(\{x|x\leq0\}\) mean. It means that x is a member of the real numbers such that x is nonnegative (0, 2/9, 1, π, 4.83333..., etc.). However, x has to be nonnegative, so it can't be -3/4, -5, -8.980333333..., etc.
I normally don't even click on these questions.. they are way outside my "comfort zone" ! ..but....I'll venture a guess......
Since it is compounded monthly...divide the annual rate by 12 (7.5/12)% = 0.625% = 0.00625
At the end of each month..there will be (1.00625 * the amount of money in the account before the company adds any that month ) in the account.
Call the monthly deposit " m "...
the amount of money after 1 month = 1.00625m
the amount of money after 2 months = 1.00625( 1.00625m + m )
the amount of money after 3 months = 1.00625( 1.00625(1.000625m + m) + m )
= 1.00625^3m+1.00625^2m +1.00625m
= m(1.00625^3 + 1.00625^2 + 1.00625)
= \(m*\sum \limits_{i=1}^{3}(1.00625^i)\)
So..after 144 months...or 12 years...there will be...
\(m*\sum \limits_{i=1}^{144}(1.00625^i)\)
Set this equal to 157,000
\(m*\sum \limits_{i=1}^{144}(1.00625^i)=157,000 \\~\\ m=157,000/(\sum \limits_{i=1}^{144}(1.00625^i))\)
And according to WA... m = 671.26
Now surely this must be a way over-complicated way of doing it..and it might be way wrong!! But...I tried!!