1)4а^2b^2-с^2
2)16-9x^2y^2
N375
25а^2-b^2=(5а-b)(5a+b)
9x^2-16у^2=(3x-4у)(3х+4y)
N380
(Х^n+y^n)(х^n-у^n)=х^(2n)-у^(2n)
Ax²+bx+c=0
x₁+x₂=-b/a
x₁x₂=c/a
5x²-2x-1=0
x₁+x₂=2/5
x₁x₂=-1/5
(x₁+x₂)²=x₁²+x₂²+2x₁x₂=(2/5)²
x₁²+x₂²-2/5=4/25
x₁²+x₂²=14/25
!x₁-x₂!=√(x₁-x₂)²=√(x₁²+x₂²-2x₁x₂)=√(14/25+2/5)=√(24/25)=√24/5