Questions   
Sort: 
Jan 29, 2021
 #1
avatar
+1

This question is extremely tough, and I had to think about this one for a while before I was able to come up with any answer at all.

 

First, we need to simplify this equation because there is a lot of simplification that is possible. I will do this by converting as many bases as possible to common bases so that the equation is easier to digest.

 

\(12^a*18^b=6^{a+2}*27^b\\ (6*2)^a*(9*2)^b=6^a*6^2*(9*3)^b\\ 6^a*2^a*9^b*2^b=6^a*36*9^b*3^b\\ 2^a*2^b={\color{red}36}*3^b\\ 2^a*2^b={\color{red}2^2*3^2}*3^b\\ \frac{2^a*2^b}{2^2}=3^b*3^2\\ 2^{a+b-2}=3^{b+2} \)

 

I simplified this equation as much as possible to see if I could make a breakthrough. With nasty equations like this one, it often best to make a key observation. This key observation will lead you to find the answer quite straightforwardly. In order to make this key observation. To make this observation, I simplified this equation a little bit more. Let's consider \(2^x=3^y\). Is there a value of x and y that will make this equation hold true? If you think about it, then the answer might jump right out at you: x = 0 and y = 0. There are no other options because the bases are different. 

 

If \(2^{\color{red}0}=3^{\color{blue}0}\) and \(2^{\color{red}{a+b-2}}=3^{\color{blue}{b+2}}\), then by parallel structure of these equations, \({\color{red}a+b-2=0}\text{ and }{\color{blue}b+2=0}\). This is a simple system of equations, so solving this will not be too difficult.

 

\(b+2=0\\ b=-2\\ a+b-2=0\\ a-2-2=0\\ a-4=0\\ a=4\)

 

Therefore, the only unique pair of integers is \(a=4\text{ and }b=-2\)

.
Jan 29, 2021
 #5
avatar
0

This is an excellent question, and I had a similar question when I was first learning. Let's investigate together! Curiosity leads to some interesting results sometimes.

 

\(x^2=y^2\\ x^2-y^2=0\\ (x-y)(x+y)=0\\ x-y=0\text{ or }x+y=0\\ x=y\text{ or }x=-y\)

 

With some algebra, we have just proven that x may equal y OR x may equal -y. This should make sense if you think about it.

I will pick an arbitrary value for y, 5.

 

\(x^2=5^2\\ x^2=25\)

 

There are two answers to this particular equation, x=5 or x=-5, even though y=5 in both cases. This is exactly what the previous algebra told us, as well.

 

We can take this question another step further, too! Let's think about \(x^3=y^3\). Does this mean that \(x=y?\). Let's employ the same factoring strategy to see if this is the case.

 

\(x^3=y^3\\ x^3-y^3=0\\ (x-y)(x^2+xy+y^2)=0\)

 

Once again, there are two factors. One is an irreducible quadratic, and the other is the familiar (x-y). Let's solve this equation.

 

\(x-y=0\\ x=y\)

 

This is a result that we expected. We already know that if you start with the same number that their cube will be equivalent. What is the other mysterious result, you may ask? Well, let's see.

 

\(x^2+xy+y^2=0\)

 

This quadratic is not factorable unfortunately, so we will have to employ creative algebra to understand this factor. I will multiply this equation by 2 to achieve

 

\(2x^2+2xy+2y^2=0\\ {\color{red}{x^2+2xy+y^2}}+x^2+y^2=0\\ {\color{red}{(x+y)^2}}+x^2+y^2=0\)

 

 

Notice how the lefthand side of this equation are all quantities that are squared and added together. Squared quantities are always nonnegative, and the only way the addition of nonnegative value can yield 0 is if the quantity that was squared was 0. Therefore, the only possible solution to this equation is that x = 0 and y = 0. That's it! In this particular case x = y, so we already had this situation covered anyway.

 

Therefore, if \(x^3=y^3\), then \(x=y\). We should note that this property only holds for the real number set.

 

We can go further once more to \(x^4=y^4\), but I think you understand the idea. I hope this aroused your curiosity!

Jan 29, 2021
 #1
avatar
0
Jan 29, 2021
 #1
avatar
0

I think I will do one of these, and you should be able to complete the rest of these because the process does not change significantly with each problem anyway.

 

\(f(x)=A\left(\sin\left[B(x-C)\right]\right)+D\\\) is the general form of a sine curve where \(|A|\) is the amplitude, \(\frac{2\pi}{|B|}\) is the period (also known as frequency), C = horizontal shift, and the equation of the midline is \(y=D\).

 

Let's put all of this information to use to do all these problems.

 

The amplitude is specified to be 6, so let's solve for the amplitude.

 

\(|A|=6\\ A=\pm6\\ A=6\)

 

We only need one sine curve that satisfies the conditions, so I will just favor the positive answers, if I can help it.

 

The period (or frequency is \(\frac{18}{\pi}\)), so let's figure out what \(B\) should be.

\(\frac{2\pi}{|B|}=\frac{18}{\pi}\\ |B|=\frac{\pi^2}{9}\\ B=\pm\frac{\pi^2}{9}\\ B=\frac{\pi^2}{9}\)

 

Once again, I will just get rid of the negative answer as we do not need it.

 

The midline occurs at y = 3, so \(D=3\).

 

Just by chance, the sine function with its current parameters already intersects the y-intercept at (0, 3), so there is no need to do a horizontal shift of any kind.

 

Therefore, the equation of this particular sine curve is \(f(x)=6\sin(\frac{\pi^2}{9}x)+3\)

 

To be honest, I am a tad puzzled with "the function is not a reflection of its parent function over the x-axis" requirement. I am not sure what this means, but I am pretty sure that this curve satisfies this cryptic condition.

Jan 29, 2021

0 Online Users