There would be 12 people at the party!
In general, with n+1 people, the number of handshakes is the sum of the first n consecutive numbers: 1+2+3+ ... + n.
Since this sum is n(n+1)/2, we need to solve the equation n(n+1)/2 = 66.
This is the quadratic equation n2+ n -132 = 0. Solving for n, we obtain 11 as the answer and deduce that there were 12 people at the party.
Since 66 is a relatively small number, you can also solve this problem with a hand calculator. Add 1 + 2 = + 3 = +... etc. until the total is 66. The last number that you entered (11) is n.
Hope this helps!
Sorry for the hand writing. But you want to factor out a 4y^2 which will result in (9y^2-1). Then you will factor out the equation in parentheses to (3y-1)(3y+1). Don’t forget to put the 4y^2 out front!
I didn't really know whatnu were asking so i took a guess..sorey if i didn't help
The slope can be calculated with the following formula:

In this case, you have the following points:
Answer:
m= 9/5 n - 3
Step-by-step explanation:
Let's solve for m.
−5m+9n=15
Step 1: Add -9n to both sides.
−5m+9n+−9n=15+−9n
−5m=−9n+15
Step 2: Divide both sides by -5.
-5m/-5 = -9n+15/-5
m= 9/5 n - 3