1)(х^2-2^2)+(х^2-3^2);
2)(а^2-1^2)+(а^2-2^2);
3)(а^2+2а+2)+(а^2+7а+12)…
(4-y-1)(4+y+1)=(3-y)(5+y)
(p-9)(p+9)
(b-1,1)(b+1,1)
(7-2+x)(7+2-x)=(5+x)(9-x)
2.cosx -cos²x=0
cosx(2-cosx)=0
a)cosx=0, x=π/2+k.π , k∈Z
b)2-cosx=0, cosx=2, /cosx/≤1, x∈∅
x=π/2+k.π, k∈Z
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An=a1+d(n-1)
0,5=3,5+6d
-3=6d
D=(-0,5)
Cos(arcsin 1) = cos π\4 = √2 \ 2