Answer:
d=2.5
Step-by-step explanation:
first find the coordinate of B(mid point of AC):A(3,7) C(6,11)
d=√(6-3)²+(11-7)²
d=√3²+4²
d=√9+16=√25=5
since B is the mid point : d/2=5/2=2.5
<h2>Another way :</h2>
B(x1+x2/2 , y1+y2/2)   , x1=3 , x2=6, y1=7, y2=11
B(9/2,18/2)
B(9/2,9)
Find AB : the length or distance between 2 points:
d=√(x2-x1)²+(y2-y1)²
d=√(3-9/2)²+(7-9)²
d=√(-3/2)²+(-2)²
d=√1.5²+4
d=√6.25
d=2.5
 
        
             
        
        
        
Answer: 
Work Shown:

This can be rewritten into 
 
        
             
        
        
        
It's called an obtuse angle.
        
                    
             
        
        
        
An irrational number/value is one you cannot express in terms of a ration, or a fraction, it cannot be written as fraction
now 291.87... is simple, two decimals, so you use two zeros at the botom and end up with 

 and boom, there you are, a fraction, nice and dandy
now, let's see the first one -√(127)  well, low and behold, 127 is a prime number, and and thus is has no two factors that'd serve as root, so, there's no rational root that'd give that, that makes it irrational
 
        
        
        
<span><span>(<span>7y+2<span>y2</span>−7</span>)</span>−<span>(<span>3−4y</span>)</span></span>
<span>=<span>7y</span><span>+4y</span>+2<span>y2</span><span>−7</span><span>−3</span></span>
<span>=11y−2<span>y2</span>−<span>10</span></span>
Hope this helps