Question

Can you please solve a it is so important

Answer 1

f(x)=-x2+5n
g(x)=-2n+15
A(x)=|g(x)-f(x)|=|x2-7n+15|
x2-7n+15>0 for every x (1)
A(x)=x2-7n+15

(1):
x2-7n+15=(x-3.5)^2-12.25+15=(x-3.5)^2+2.75 > 0
because for every x: (x-3.5)^2>=0

answer: A(x)=x2-7n+15