Question

State whether the equation is a linear equation in one variable or not. –2x(–2 – x) = x + 1

Answer 1

If you'll simplify this equation -2x(-2-x)=x+1
you'll get 4x+2x²=x+1
simplify further 2x²+3x-1
this one looks like a quadratic equation.
Thus, this is not a linear equation,

Answer 2

$-2x(-2 -x) = x + 1\\ 4x+2x^2=x+1$

It's not linear. It's quadratic.