Ok, answering this question requires some knowledge of functions.
\(f(x)=3x^2-2x+4\)
\(g(x)=x^2-kx-6\)
When the question asks what is f(10)-g(10), the question is asking what the functions equal to when x=10.
Let's do just that first. I'll evaluate them separately.
\(f(x)=3x^2-2x+4\) | Evaluate the function for f(10), which means make all instances of x into a 10. |
\(f(10)=3*10^2-2*10+4\) | We must be mindful about our order of operations here. First, do the exponent first. |
\(f(10)=3*100-2*10+4\) | Let's evaluate all instances of multiplication first. |
\(f(10)=300-20+4\) | Do the subtraction and addition. |
\(f(10)=284\) | |
Now, let's evaluate the other function.
\(g(x)=x^2-kx-6\) | Again, replace all instances of x with 10. |
\(g(10)=10^2-k*10-6\) | Evaluate exponents first to abide with order of operations. |
\(g(10)=100-10k-6\) | Combine the only set of like terms, 100 and -6. |
\(g(10)=94-10k\) | |
Ok, now we have to do f(10)-g(10)=10:
\(f(10)-g(10)=10\) | Replace the calculated values for f(10)-g(10) |
\(284-(94-10k)=10\) | Distribute the negative sign into the parentheses. |
\(284-94+10k=10\) | Do 284-94 to simplify the lefthand side. |
\(190+10k=10\) | Subtract 190 on both sides of the equation. |
\(10k=-180\) | Divide by 10 on both sides. |
\(k=-18\) | |
Ok, I am done now!
Ok, I will assume for this problem that the 5 is labeled in inches, even though it does not say in the diagram. Yet again, I'll attempt to create a makeshift diagram like I did for you before.
A 5in B
------------------------------------------------
/ | | \
/ | | \
/ | (2*sqrt(3))in | \
/ | | \
/ | | \
--------------------------------------------------------------
D E F C
Let's remember what an altitude is; an altitude is the height that runs perpendicularly from a base to a vertex of the figure. Therefore, \(m\angle AED =90^{\circ}\). We already know that \(m\angle D=60^{\circ}\) by the given info. Of course, by the triangle sum theorem, \(m\angle DAE=(180-(90+60))^{\circ}=30^{\circ}\).
What does this mean? We have identified a 30-60-90 triangle in the diagram, and that is a special one! Let me explain with a diagram:
Source: http://study.com/cimages/multimages/16/30-60-90-example-diagram.png
This diagram shows the relationship between the sides and the angle measures.
1) The angle across 30 is x
2) The angle across 60 is \(x\sqrt{3}\)
3) The angle across the right angle is 2x.
This means that the ratio of the sides of a 30-60-90 triangle is \(1:\sqrt{3}:2\). Let's use this information to solve for some missing sides.
\(DE\sqrt{3}=AE=2\sqrt{3}\) | This is the ratios of the side lengths determined above. |
\(DE\sqrt{3}=2\sqrt{3}\) | Divide by \(\sqrt{3}\) on both sides. |
\(DE=2\) | |
We have determined the length of DE, 2. Now, let's determine the length of the hypotenuse of \(\triangle ADE\) by using the ratio of the side lengths.
\(2DE=AD\) | Substitute the value that we calculated for DE, 2. |
\(AD=2*2=4\) | |
Note that the same relationship occurs for the other triangle, \(\triangle BFC\), so \(FC=2\) and \(CB=4\). There is only one length we haven't determined the length of. It is \(EF\).
The length of this is right in front of us! \(AB=EF=5\). Now, add all of these together!
\(P=(5+4+2+5+2+4)in\) | Add these lengths together to get the final perimeter of the trapezoid, in inches. |
\(P=22in\) | |
Bam! Done!
Do you mean \(2-x-2=4\)?
If so, I will solve it as so:
\(2-x-2=4\) | Combine the like terms on the left hand side of the equation |
\(-x=4\) | Divide by -1 on both sides to get rid of the negative on the x. |
\(x=-4\) | |
If you are ever unsure if you have the correct value for your unknown, just plug it back into the equation:
\(2-(-4)-2=4\) | Check to see if this is true; if it is wrong, you either made a mistake or you have an extraneous solution. |
\(2+4-2=4\) | Subtracting a negative number is the equivalent of adding a positive one. |
\(6-2=4\) | |
\(4=4\) | 4=4 is a true statement and concludes that the value for x is correct. |
If you are going to list decimals, I would highly advise separating them with commas, as opposed with a numbered list. The decimals are confusing to read. If you want to use a numbered list still, I would do what I did below.
This is how I would revise your question:
Write each decimal as a fraction in simplest form.
1) 0.222
2) 0.1515
3) .0242424
4) 0.5555
5) -0.124124124
This is what I perceive the intended decimals to be, but I am not entirely sure, so correct me if I am wrong.
I will start with the first decimal, 0.222.
\(0.222\) | First, identify what place the decimal extends until (in this case, it extends to the thousandths place) and set it equal to a fraction over 1000. |
\(0.222=\frac{222}{1000}\) | Now, identify the GCF of the fraction. It is harder with larger numbers, but both numbers are even, so we can, at least, divide by 2. |
\(\frac{222}{1000} \div \frac{2}{2}=\frac{111}{500}\) | 111 and 500 do not share any common factors, except for 1, so this fraction is in simplest form. |
I will do the next decimal, 0.1515
\(0.1515\) | Do the same process as above; the decimal extends until the ten thousandths place. Set it to a fraction over that amount, ten thousand. |
\(0.1515=\frac{1515}{10000}\) | Yet again, it can be hard to determine the GCF, but both numbers end in a 5 or 0, so both are divisible by 5. |
\(\frac{1515}{10000}\div \frac{5}{5}=\frac{303}{2000}\) | Yet again, there are no common factors greater than 1, so this fraction is irreducible. |
I will do the next decimal, as well.
\(0.0242424\) | This extends to the ten millionth place, so put the number over a fraction over ten million. |
\(0.0242424=\frac{242424}{10000000}\) | The numerator and denominator's final two digits are divisible by 4, so we can divide them by, at least, 4. |
\(\frac{242424}{10000000}\div\frac{4}{4}=\frac{60606}{2500000}\) | We aren't done yet. The numerator and denominator are both even, so it is divisible by 2. |
\(\frac{60606}{2500000}\div\frac{2}{2}=\frac{30303}{125000}\) | The numerator and denominator are co-prime, so this fraction is in simplest form. |
Here goes the next one:
\(0.5555\) | The decimal extends to the ten thousandths place, so make a fraction over ten thousand. |
\(0.5555=\frac{5555}{10000}\) | Both the numerator and denominator are divisible by 5 because both of them end in a 5 or a 0. |
\(\frac{5555}{10000}\div \frac{5}{5}=\frac{1111}{2000}\) | 1111 and 2000 have no common factors, so the fraction is simplified completely. |
And, of course, here is the next one, -0.124124124.
\(-0.124124124\) | This decimal extends to the billionth place, so set it over a billion. Just put the negative sign in front of the fraction. |
\(-0.124124124=-\frac{124124124}{1000000000}\) | Both the numerator and denominator's final 2 digits are divisible by 4, so the fraction can be simplified. |
\(-\frac{124124124}{1000000000}\div\frac{4}{4}=\frac{31031031}{250000000}\) | There are no more common factors. |
You are done now!