№1.
7x²-28=7(x²-4)=7(x-2)·(x+2)
3a³-108a=3a·(a²-36)=3a·(a-6)·(a+6)
3x²-48xy+192y²=3(x²-16xy+64y²)=3(x-8y)²
-75a⁶+30a⁴-3a²=-3a²·(25a⁴-10a²+1)=-3a²·(5a²-1)²
x²+2xy+y²-64=(x+y)²-64=(x+y-8)·(x+y+8)
№2.
7x³-28x=0
7x·(x²-4)=0
x·(x²-4)=0
x=0
x=0
x²-4=0
x=-2
x=2
x₁=-2
x₂=0
x₃=2