# Thread: 8 problems that I can't understand after trying for days and looking examples online

1. ## 8 problems that I can't understand after trying for days and looking examples online

Hello. We got an assignment of 105 math problems. I solved them all except the ones I wrote on a sheet of paper and took a picture. If anyone can help me with ANY ONE OF THESE, I'll be very grateful. This is a study review and I need to have the solutions so I can study for my tomorrow's test (if I have an example of a problem, I can interpret it then). And it's not that I'm studying the last day, I studied all other problems that I've solved by myself, but these ones I just can't and believe me, I tried to understand them.

2. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

Originally Posted by Heisenberg
Hello. We got an assignment of 105 math problems. I solved them all except the ones I wrote on a sheet of paper and took a picture. If anyone can help me with ANY ONE OF THESE, I'll be very grateful. This is a study review and I need to have the solutions so I can study for my tomorrow's test (if I have an example of a problem, I can interpret it then). And it's not that I'm studying the last day, I studied all other problems that I've solved by myself, but these ones I just can't and believe me, I tried to understand them.

It is unexcused of you to be so lazy as to not be willing to type out these questions.

You are also to lazy to insure that the images that you posted are readable.

3. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

There's some truth in what Plato says, but I'll try to help a little. These problems, though they may seem simple enough to some of us, are tedious and time-consuming.

Question number 2: If you try graphing it out, using a sample value for g like 2 or 3, you'll see that the result is symmetric with respect to the x axis. The only effect of the constant g is to move the horizontal parabola along the x axis.

Question 6: Your handwriting is a little confusing. It took me a while to figure out that you write "one" to look like "seven." In part c, rewrite both sides as powers of 5 (eg 625 is 5 cubed, 3125 is 5 to the fourth power) and then the answer should fall out. In part b, but everything in powers of 3, then multiply by 81, which is what power of 3? You should know.

Question 7: Treat each side as an exponent, raise h to that power. You should wind up with a quadratic equation.

Good luck in your test. Look, math isn't that hard if you approach it with the right attitude, but sometimes it will be tedious. Be prepared for that.

4. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

Not trying to be venomous, but this is the last kind of topic with which I am inclined to help. If I have to work harder than the OP, then something is wrong.

For me, these are the major points of contention:

a) Attached are images of hard to read hand-written work. I can understand attaching images if the problem is accompanied by hard to recreate diagrams. These problems would be easy to type out, and taking a few mintes to do so would make it much easier to read them.

b) The images are oriented sideways. Why?

c) There is a multitude of problems.

d) No work shown. Surely you have some thoughts or attempts at the problems?

5. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

I'm not disagreeing exactly, but OP does claim that s/he is giving us only a fraction of the original problems assigned, and that s/he worked hard solving the others. Also, remember this is the first post ever, maybe s/he needs a little time to learn how we think.

I hope you, the OP, won't be afraid to ask more questions or to try to help others when you can. Just prepare your posts a little better, OK?

Learning Latex is a good idea. I'm just beginning at that myself.

6. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

Question 1:
The general equation of a circle is given by $\displaystyle (x-m)^2 + (x-n)^2 = r^2$, whereby $\displaystyle (m,n)$ is the circle's midpoint.
Step 1: Find the midpoint.
$\displaystyle (m,n)=\left(\tfrac{x_2+x_1}{2},\tfrac{y_2+y_1}{2})$
Step 2: Compute the distance, $\displaystyle d$, between the two diameter endpoints. This gives the diameter, which is twice the radius.
$\displaystyle d = \sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$
Step 3: Plug it all in.
$\displaystyle (x-m)^2 + (x-n)^2 = (\tfrac{d}{2})^2$

7. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

@zhandele, you were right, seems like you're the only who read my post. I'm definitely not lazy, it's just that I searched online and looked in books for the problems that I wrote, and I couldn't do them because I didn't understand them. Those who doubt that I did any work, I posted a video on Youtube, showing my work and showing the problems that I posted here. Link: My math work for mathhelpforum.com / user: Heisenberg - YouTube

As for typing my problems here, how would I do that? For example, how do I write y(square) for example? Simple reason for photos is that I thought it'd be more readable and not because of laziness. And why are they sideways? They are correct way in my computer, so that's not my fault.

And zhandele was right, it's my first post, and I got a lot to learn on how you guys think.

@zhandele, thank you for your help very much. And yes, of course I'll help when I can.

Edit: @abender, thank you million times!

8. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

Question 2:
Is there symmetry with respect to the x-axis? Substitute $\displaystyle -y$ in your equation for $\displaystyle y$. If the equation does not change, there is symmetry with respect to the x-axis.
$\displaystyle (-y)^2-9=x \text{ is the same as } y^2-9=x$, so there IS symmetry with respect to the x-axis.
Is there symmetry with respect to the y-axis? Substitute $\displaystyle -x$ in your equation for $\displaystyle x$. If the equation does not change, there is symmetry with respect to the y-axis.
$\displaystyle y^2-9=-x \text{ is NOT the same as } y^2-9=x$, so there is NOT symmetry with respect to the y-axis.

For the last one, perform the same process, but substitute $\displaystyle -x$ for $\displaystyle x$ AND $\displaystyle -y$ for $\displaystyle y$.

Good luck!

9. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

I did read your post in its entirety. When you have been on math forums for a while, you have heard it all. I'm not saying you are lazy in general by any means, but when I see attached sideways images of 8 hand-written problems with no accompanying work, I am inclined to move on. I can assure you I am not the only one who feels this way. I love to help, but when I see such a minimal effort on the part of the OP to present the problems, I don't feel this warrants much effort if any on my part.

Now, I am not trying to come down on you, but rather offer constructive criticism that will help you garner help in the future.

10. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

Question 5:

To find an inverse, write out the function, replacing $\displaystyle f(x)$ on the left-hand side with $\displaystyle y$. Then, change $\displaystyle x$ to $\displaystyle y$ and $\displaystyle y$ to $\displaystyle x$. Solve in terms of $\displaystyle y$. Clear enough?

11. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

Question 5 is clear. However, my result doesn't come up like in the solutions. The result in solutions is the one in the picture. Again, I didn't know how to write the f(-1).

12. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

Question 8:

Write as the sum and/or difference of logs: $\displaystyle \log_{15}\frac{\displaystyle^8\sqrt{7}}{y^x}$

Did I copy this one down correctly?

13. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

It's correct, only thing missing is "square".

Bottom thing is y-square x

14. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

Originally Posted by Heisenberg
Question 5 is clear. However, my result doesn't come up like in the solutions. The result in solutions is the one in the picture. Again, I didn't know how to write the f(-1).
$\displaystyle f(x)=(x-2)^3$

$\displaystyle y=(x-2)^3$

Switching $\displaystyle x$ and $\displaystyle y$:
$\displaystyle x = (y-2)^3$

Now, to solve for $\displaystyle y$, raise both sides to the $\displaystyle \tfrac{1}{3}$ power:
$\displaystyle x^{\frac{1}{3}} = ((y-2)^3)^{\frac{1}{3}}$

$\displaystyle x^{\frac{1}{3}} = y-2 \implies y = x^{\frac{1}{3}}+2$

REMEMBER, the cube root is the same as the one-third power, just like the square root of a number is the same as the number raised to the one-half.

15. ## Re: 8 problems that I can't understand after trying for days and looking examples onl

Originally Posted by Heisenberg
It's correct, only thing missing is "square".

Bottom thing is y-square x
Do you mean $\displaystyle y^{2}x$?

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