Question 320117
Post one question at a time or else no one will reply.

(1) x^2 = 16

Let sqrt = square root for short

sqrt{x^2} = sqrt{16}

x = 4

Done! 

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(2) x^2 - 36 = 0

Add 36 to both sides.

x^2 - 36 + 36 = 0 + 36

x^2 = 36

Take square root of both sides.

sqrt{x^2} = sqrt{36}

x = 6

Done!

Now post questions 3 and 4 individually.