Question

16x2 – 81 = 0

Answer 1

try \((4x+9)(4x-9)=0\)

Answer 2

as
\[16x^2-81\] is the difference of two squares \(a^2-b^2=(a+b)(a-b)\)

Answer 3

alternatively you would write
\[16x^2=81\] so
\[4x=9\] or \[4x=-9\]

Answer 4

or even
\[16x^2=81\implies x^2=\frac{81}{16}\implies x=\pm\frac{9}{4}\]

Answer 5

lots of ways to skin this cat