How do you solve #x^2-9=0#?

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Answer 1 · 2016-04-28T09:22:41

#x=-3# or #x=3#

In #x^2-9=0#, add and subtract #3x#, this leads to

#x^2+3x-3x-9=0#

or #x(x+3)-3(x+3)=0#

or #(x-3)(x+3)=0#

As product of #x+3# and #x-3# is zero,

either #x+3=0# or #x-3=0#

i.e. #x=-3# or #x=3#