RadicalX^2-25=12
Rad169-x^2=12
Radx^2-4=8

1.

-25 + x = 12

x - 25 = 12

x - 25 + 25 = 12 + 25

x = 37.

2. -x²+13 = 12

-x²+13-22=12-12

(x+1)(-x+1) = 0

x = {-1, 1}.

3.

-4 + x = 8

x - 4 = 8

x - 4 + 4 = 8 + 4

x = 12.

√(x²-25)=12 ridici  cegalitatea     la     patrat

x²-25=12²

x²=25+144

x²=169

x=√169==+/-13

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√169-x²=12   ridici     egalitatea    la    patrat

169-x²=12²

169-x²=144

-x²=144-169

-x²=-25

x²=25

x=√25=+/-5

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√(x²-4)=8

x²-4=8²

x²-4=64

x²=64+4

x²=68

x=√68=√4*17=2√17