Question

Simplify the expression

Answer 1

`\bf (-9\cdot i)(-9\cdot i)\implies -9i\cdot -9i\implies +9^2i^2\implies 81i^2 \\\\\\ 81(√(-1)\cdot √(-1))\implies 81(√((-1)^2))\implies 81(-1)\implies \boxed{-81}`