100, because, x^2 - 20x + 100 = ( x - 10 )^2;
A(n)=a(1)+d(n-1), d=a(16)-a(15)=-5-(-53)=48
a(15)=a(1)+d*(15-1),
-53=a(1)+48*(15-1),
a(1)=-53-48*14= -725
a(n)=-725+48(n-1)
Triangle classification by sides would be scalene, no congruent sides; isosceles, at least 2 congruent sides; equilateral, 3 congruent sides.
If half of two acres was planted with green beans, the answer would be one acre