<p>Hello, these are the math problems that I need help with: (Blue Book, Test 5, Section 7)</p>
<p>18)If the sum of the consecutive integers from -22 to x, inclusive, is 72, then what is x?
a) 23
b) 25
c) 50
d) 75
e) 94</p>
<p>19)If k, n,x and y are positive numbers satisfying x^-4/3 = k^-2 and y^4/3 = n^2, what is (xy)^-2/3 in terms of n and k?
a)1/nk
b) n/k
c) k/n
d) nk
e) 1</p>
<p>20) Has graphs and crap so I can't type it out.</p>
<p>Thanks!!</p>
<p>18) is b (25)</p>
<p>because the sum between -22 and 22 = 0 and the sum of 23, 24, and 25 = 72</p>
<p>The key is to get both x and y to have an exponent of -2/3 so you can sub in k and n.</p>
<p>x^(-2/3) would be k^(-1) and y^(-2/3) would be n^(-1)</p>
<p>(xy)^(-2/3) = k^(-1) * n^(-1) or A.</p>
<p>for 20, take a point on each graph
f(x) (-1,3) and g(x) would be (2,1)</p>
<p>how do you get from -1 to 2? you are moving RIGHT 3 so you have to subtract 3 (-3).
how do you get from 3 to 1? you are moving DOWN 2 so you have to subtract 2 (-2)</p>
<p>-3 * -2 is 6 or E.</p>
<p>can someone explain number 18 again plz?</p>
<p>Q.8 - The sum of the numbers is positive so x will have to be greater than 22 because in order to cancel out -22 you'll need a 22 similarly to cancel the -21 you'll need a 21 and so on.So the sum from -22 to 22 will be 0.after that you continue to add the next numbers until you get the desired sum.i.e. 23+24=47+25=72. The last number you added was 25 so x =25.</p>
<p>There is this cool place to look for the explanations:
<a href="http://talk.collegeconfidential.com/sat-preparation/339734-consolidated-list-blue-book-math-solutions-3rd-ed.html%5B/url%5D">http://talk.collegeconfidential.com/sat-preparation/339734-consolidated-list-blue-book-math-solutions-3rd-ed.html</a>
673 / 18 is there too.</p>
<p>Thanks everybody for the responses, they really helped. The only one I still don't understand is #20. Would somebody mind trying to explain this thoroughly with the thought process? Thanks again.</p>
<p>the equation for a parent function would be
(x-h)+k</p>
<p>h determines if it moves < or >
k determines if it moves ^ or v</p>
<p>a specific point on f(x) and g(x) that corresponds would be (-1,3) and (2,1)
now go back to the equation (x-h)+k</p>
<p>on the x coordinate, you are going from -1 to 2 so you are moving right 3.
on the equation, plug it in. (x-(3))+k</p>
<p>but wait! when you plug it into the equation, the equation changes it to a negitive number.</p>
<p>thats where I got the -3 from.</p>
<p>do the same for the y axis. 3 to 1 would mean moving down 2; plug it into the equation</p>
<p>(x-(3))+(-2) which equals (x-3)-2</p>
<p>now it asks you for hk, so h=-3 and k=-2</p>
<p>o_O its 6 :D!</p>
<p>excuse me but in the USA don't you study aritmetical and geometrical progressions? What are that stupid solutions for 18?! If you have that the sum of all integers between 23 and x is 1245 what would you do?!</p>
<p>Ok, thanks for that explanation of 20, I get it now. :)</p>