Question

x2 = 16, therefore x = 4. Is this a valid conclusion? If no, give a counterexample

Answer 1

False. What other value squared = 16 other than 4? It will be your counterexample.

Answer 2

Postitive thinking is good for mental health but negative thinking in mathematics sometimes pays off if you think about negative numbers. (strong hint)

Answer 3

imaginary thinking works best for me.

Answer 4

She promised to do this but left. The counterexample is -4.
x2 = 16
x^2 - 16=0
(x + 4)(x -4) = 0
x = -4 or x = -6.
Every number has two square roots.