If we can write
[tex]5x^2 + nx + 48 = (ax + b) (cx + d)[/tex]
then expanding the right side gives
[tex]5x^2 + nx + 48 = acx^2 + (ad+bc)x + bd[/tex]
so that [tex]ac=5[/tex], [tex]ad+bc=n[/tex], and [tex]bd=48[/tex], where [tex]a,b,c,d[/tex] are integers. We want to maximize [tex]ad+bc[/tex].
5 is prime, so [tex](a,c)[/tex] can be either (1, 5) or (5, 1). Let [tex]a=5[/tex] and [tex]b=1[/tex]. Then maximizing
[tex]ad+bc=5d + c[/tex]
is just a matter of picking the largest possible value for [tex]d[/tex], which is 48. Then [tex]\max\{ad+bc\}=5\times48+1\times1=\boxed{241}[/tex].
