(7n+8,5)²-(4n+2,5)²=(7n+8,5+4n+2,5)*(7n+8,5-4n-2,5)=(11n+11)*(3n+6)=
=11*(n+1)*3*(n+2)=33*(n+1)*(n+2).
Решение смотри во вложении
1. x< -2,4
-24 - 10x = x^2
x^2 + 10x + 24 = 0
По теореме Виета
x1 = -6
x2 = -4
2. sqrt(98)*sqrt(8) - sqrt(50)*sqrt(8) = sqrt(98*8) - sqrt(50*8) = 28 - 20 = 8