0
x^2 - 4 = 0
What you have to recognise is that the constant '4' is a 'squared number.
4 = 2^2
So we can write
x^2 - 2^2 = 0
Next remember that two squared terms with negative between then, factors.
Hence
x^2 - 2^2 = 0
=>
( x - 2)(x + 2) = 0
NB Note the plus (+) sign in the second bracket.
Hence
x - 2 = 0
x = 2
&
x + 2 = 0
x = -2
So 'x' can take two values, they are '(+)2, & -2'.
NB Note that two squared terms with a plus(+) between then , does NOT factor. e.g. the Pythagorean equation. c^2 = a^2 + b^2
lenpollock
Wiki User
∙ 13y agoIf x2 - 4 = 0 then x2 = 4
⇒ x = 2 or x = -2.
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