1) =2p²+2q²+4pq-4pq+p²+q²=3p²+3q²
2)=( b²-a²)(b²+a²)=b⁴-a⁴
3)=n²-9t²+n²-4t²-2n²+13t²=0
x²-5x-50<0
x²-5-50=0 D=225 √D=15
x₁=10 x₂=-5 ⇒
(x-10)(x+5)<0
-∞_____+_____-5_____-_____10_____+_____+∞
Ответ: x∈(-5;10).