Answer:
66
Step-by-step explanation:
If there are <em>n</em> students, then the number of pairs is 
.
With 12 students, 
pairs can be formed.
The reason the formula works is this: Each of the 12 students can be paired with 11 other students (no student is paired with him/her self). But counting 12 x 11 = 132 counts each pair <u>twice</u>. Example: student A can be paired with student B,..., student B can be paired with student A. The pair was counted two times.
See the attached image that shows pairings of 5 students. There are
5(5 - 1)/2 = 5(4)/2 = 10 pairs.
Answer:
y = -2x^2 - 4x - 1
Step-by-step explanation:
We can see that the graph passes through (-2, -1), (-1, 1) and (0, -1).
Let's solve
ax^2 + bx + c = y
a(-2)^2 + b(-2) + c = -1
4a - 2b + c = -1
a(-1)^2 + b(-1) + c = 1
a - b + c = 1
a0^2 + b0 + c = -1
c = -1
we got c = -1 so we input it into the other 2
4a - 2b - 1 = -1
4a - 2b = 0
2a - b = 0
2a = b
a - b - 1 = 1
a - b = 2
a = b + 2
Let's input b = 2a
a = 2a + 2
-a = 2
a = -2
b = 2a = 2*(-2) = -4
c = -1
y = -2x^2 - 4x - 1
If Maya only has $15 dollars to spend and she buys a notebook for $5.50 then that leaves her with $9.50 and if she has to save $7.75 then that leaves her with $1.75 and since she wants to buy cookies then you have to figure out how many cookies she can get with $1.75 plus the tax but food doesn't have tax so she can buy 7 packages of cookies since there only 25 cents is right on point at $1.75 I hope I answered your question with all the calculating I had to do and the typing I went through to explain it to you !!!!!!!!!!!!!!!!!!!!!!!! now could you please give me a thank you and hit the brain aster button please and thank you so much
if you do !!!!!!!
