А1=-36, d=2
a21=-36+40=4
s21=-36+4/2*21=420
(x-y)/(x^(1/2)-y^(1/2))=(x^(1/2) - y^(1/2))((x^(1/2)+y^(1/2))/(x^(1/2)+y^(1/2))=x^(1/2)-y^(1/2)
(3^2)^х+1 -12*3^х+1 +27=0
(3^х+1)^2 -12*3^х+1 +27=0
3^х+1=t
t^2 -12t+27=0
t=9. t=3
3^x+1=9
3^x+1=3^2
X+1=2
X=1
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3^x+1=3
x+1=1
X=0
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Ответ: Х=0 Х=1
5^(Х-3)(Х+5)=5^0
(Х-3)(Х+5)=0
Х-3=0. Х=3
Х+5=0. Х= -5
Ответ: х=3; x= -5
((5k-5) / (k²-1) - k / (k+1)) : (5-k) / (k+1) = ((5k-5) / (k-1)(k+1) - k / (k+1)) :
(5-k) / (k+1) = ((5k-5) / (k-1)(k+1) - (k²-k) / (k-1)(k+1)) : (5-k) / (k+1) =
(5k-5-k²+k) / (k-1)(k+1) : (5-k) / (k+1) = (6k-k²-5) / (k-1)(k+1) : (5-k) / (k+1) =
(6k-k²-5)(k+1) / (k-1)(k+1)(5-k) = (6k-k²-5) / (k-1)(5-k) = (6k-k²-5) /
(5k-k²-5+k) = (6k-k²-5) / (6k-k²-5) = 1.