Answer:  The equation of the circle as specified is (x+5)² + (y -1)² = 25
Step-by-step explanation:  Use the Pythagorean Theorem to calculate the length of the radius from the coordinates given for the triangle location: A(-1,4), B(-1,1) and C(-5,1)  
subtract y-values of A & B 4-1=3 AB = 3
subtract x-values of B &C -5-(-1) =4 BC=4  3² + 4² = 9 + 16 = 25  
√25 = 5   AC = 5  That is the radiuus of the circle.    
The sides of the triangle are AB=3, BC=4, AC=5.
Use the equation for a circle: 
( x - h )² + ( y - k )² = r², where ( h, k ) is the center and r is the radius.
Use the coordinates of C, (-5, 1) as h and k  in the equation
Substituting those values, we have (x -[-5])² + (y -[1])² = 5²
Simplify:  (x+5)² + (y -1)² = 25
A graph of the circle is attached. The radius is AC, between the center C (-5,1) and A( -1,4) on the circumference.  (Sorry, I still need to learn how to create line segments!)