Multiply 3 to the first bracket then multiply 2 to the second bracket. 3(a+2b) + 2(3a+b) = 3a+6b+6a+2b= 9a+8b
This isn’t 30 points this is 15
16 n^2 -10n + 129 = 8n^2 -8
We collect the terms:
8n^2 -10n + 137 = 0
The steps for completing the square:
1) Move the "non X" (or "non N") term to the right:
8n^2 -10n = -137
<span>2)<span> Divide the equation by the coefficient of N² which in this case is 8
n^2 -1.2n = </span></span><span><span>-17.125
</span>
3) Take the coefficient of "N"; divide it by 2; square it; add it to both sides of the equation.
-1.2 / 2 = -.6
-.6^2 = .36
</span>
n^2 -1.2n +.36 = <span>-17.125
+.36
Take the square root of both sides:</span>
(n-.6)*(n-.6) = sq root(
<span>
<span>
<span>
-16.765
</span>
</span>
</span>
)
That's about as far as I can go.
If <em>a</em> is fixed and <em>b</em>,<em>c</em> are unknowns then the equation <em>b</em>+<em>c</em>=10-<em>a</em> has 11-<em>a</em> solutions. They are pairs (b,c): (0,10-a), (1,9-a), (2,8-a), ... (10-a,0). As <em>a</em> runs from 0 to 10 we have total number of solutions (11-0)+(11-1)+...(11-1)=11+10+...+1=(1+11)*11/2=66.
