Question 1

I saw the answer, but I couldn't tell how to indicate my answer for the correct sequence.

Accepted Answer

it may look comfusing at first, but it's all about looking at the question carefully! for example, the question that Sal was doing: it's obvious that the first line on the top won't be wrong, cause that IS the starting question! so the 1st step is  obviously the 2nd line from the top, and 2nd step is the 3rd line from the top and so on. in short, whatever line it is in that kind of form, go down one line more to find the answer. Hope I am not confusing :P

Question 2

At 1:33 in the lower left corner, what does "Sal said "square root of 11" but meant "11" " mean?

Accepted Answer

It is letting you know that when he said "square root of 11" it was a mistake and what he really meant is "11". Hope this helps.

Question 3

At 0:27 you said to try it out on your own, and I did........ The answer that I got was she did not do the negative and minus sign. Is that correct?

Accepted Answer

Yes. She didn't put those in, and therefore only got one answer. To get the correct answer, the plus/minus sign must be there.

Question 4

how do i solve x^2+8x=64=12

Accepted Answer

You need to clarify your equation.  It has two "=" symbols.  Is one suppose to be a minus?

Question 5

The question is find all the roots. But i do not understand what that means exactly. One of the the questions is x^4 + x^2 - 90. The only thing that i could think of was x^6 - 90 but not any further than that. Is there a certain formula for this or am I correct?

Accepted Answer

First, you can't add unlike terms:  x^4 + x^2 does not = x^6
Next, I assume you have an equation of `y = x^4 + x^2 - 90` or `f(x) = x^4 + x^2 - 90`
To find the roots, set y = 0 and solve for "x": `0 = x^4 + x^2 - 90`
Start by factoring.  Your polynomial is factorable into  `0 = (x^2 + 10)(x^2 - 9)`
You now have 2 quadratic factors.  You can split these into individual equations to solve:
`0 = x^2 + 10` and `0 = x^2 - 9`
Both of these are solvable using the square root method shown in this video.
See if you can finish solving them.  Note:  One creates complex roots.
If you get stuck, comment back.

Question 6

Meredith actually solved the equation correctly on all of these steps, so I thought Meredith didn't make any mistakes! Did Meredith make a mistake in any of these steps? If yes, which step did Meredith made a mistake in? If not, then what happen to the choice "Meredith did not make a mistake"?

Accepted Answer

This is an older version of KA's site.  Many exercises like this now do include an option for no mistakes.  Note:  If that option isn't one of the possible answers, then you know that Meredith *did* make a mistake.  You just have to figure out where it is.

Question 7

I need help 9(9-9x^2)= 9 I don't know how to solve this

Accepted Answer

Distribute first 9*9 - 9*9x^2 = 9, 81 - 81x^2 = 9; add 81x^2 to both sides and subtract 9, you end up with 72 = 81x^2, divide by 81 to get x^2 = 72/81, square root of both sides, you get x = ± √(72/81) which reduces to x = ±  √(8/9) = ± 2√2 / 3.

Question 8

At 0:37, what does Sal mean when Sal said "hold the equality?"

Accepted Answer

Read the transcript as a whole sentence, not just the fragment.  He is basically saying that the both sides were correctly divided by 2.  This is required to maintain the equality of the equation (keep the 2 sides in balance / equal to each other).
Hope this helps.

Question 9

Could you do the distributive property for this?

Accepted Answer

You can't use distributive property for binomials like (x-2)^2 and then making it into x^2 - 2^2. There is a plus or minus within the brackets so apparently it is not possible. The next exercise will tell you so.

But if you have something like (x*2)^2 where you're multiplying terms, then you could distribute: x^2 * 2^2

But if you have something like (x*2)^2 where you're multiplying terms, then you could distribute:   x^2 * 2^2

Algebra 1

Course: Algebra 1 > Unit 14

Quadratics by taking square roots: strategy

Want to join the conversation?

Video transcript