Question

Why is -9an acceptable answer to the equation x2=81 ?

Answer 1

Explanation:

Because square of a negative number gives a positive number, that's why - 9 is an acceptable answer to the equation
`x^2 = 81`

Answer 2

X=9 or x=-9

Explanation:

X^2=81

Can be written as

x^2-81=0

Factorize by the property:

a^2-b^2=(a-b)(a+b)

So the expression becomes:

(x-9)(x+9)=0

Therefore, either x-9=0or x+9=0

Then the solutions are x=9 or x=-9