Few Math Questions

Test Preparation SAT Preparation
1

<p>If f (x) = squared root of x2 (ex. so if u put x as 2 u would square if then square root it so it goes back to 2), then f (x) can also be expressed as</p>

<p>a) x
b) -x
c) + or - x
d) lxl</p>

<p>okay the answer is d, why isn't it c?</p>

<p>what is the radius of a sphere, with center at the origin, that passes through point (2,3,4)</p>

<p>im guessing we use distance formula but isn't that needing like x1 and x2 points? etc.</p>

<p>and lastly</p>

<p>log2 m = x and log2 n =y
so what does mn =?</p>

<p>the explanations say it becomes</p>

<p>log2 mn = x+y
2^x+y = mn</p>

<p>thanks!!!!!!!!</p>

2

<p>the first one, square root can only be pos.</p>

3

<p>yea but if u square the negative number it becomes positive
…</p>

4

<p>k what? if f(x)=sqr(2x) then how is that equal to f(x)=|x|…none of the answers make sense!</p>

<p>second one, you have points (0, 0, 0) and (2, 3, 4)…so radius is sqr(29)=~5.385.'</p>

<p>third one…i forget these log properties, guess i should relearn them lol. Is it not when you add the two loggs…log2 m + log2 n…it really means log2 mn. so thaat equals x+y.so mn=2^(x+y).</p>

5

<p>i said x2 u know x^2 not 2x lol</p>

<p>and whats the name of the log property u just did</p>

<p>and how did u get squared root of 29 for number 2
? distance formula? how do u know which one to put is o or 2 x1 or x2?</p>

6

<p>When you have points like A(a,b,c) and B(x,y,z),the distance between A and B is given by root over[(a-x)² + (b-y)² + (c-x)²].So,substitute the values in this formula.</p>

7

<p>i forget the names for the log properties…but the distance formula is sqr[(x2-x1)^2+(y2-y1)^2+(z2-z1)^2], where the two points are (x1, y1, z1) and (x2, y2, z2).</p>

<p>so yea the square root thingy should be D because whenever there is a square root sign without the + or - sign before it, automatically assume principle square root (positive root only). only if there is a + or - sign indicating otherwise does it include negative root. Also remember that if you are putting in the root, (like you have x^2=9) then include both negativ and positive roots (so x=+or- sqr(9)).</p>

8

<p>The log property is called the product property.</p>

9

<p>for number 1,
if im not mistaken, i believe u can factor out the square, so it becomes (sq rt of x)^2. it becomes clear that x has to be positive values or else u’ll get some imaginary i’s.</p>

10

<p>thanks guys
but for the question pretend i work it out
(squared root of x^2)
ill use three…
so i square three so its squared root of 9
when i work that out it becomes

  • or - x</p>

<p>so how come c can’t work?
when u square root u always take positive and negative sdie</p>

11

<p>^ i already explained all of this.</p>

<p>

</p>

12

<p>read the explanations again bro</p>

13

<p>oh ok
thanks i got what u guys meant
the principle square root rule
and etc.</p>