If x is zero then you must replace x with zero and use the rules of PEMDAS (Parentheses, Exponent, Multiplication, Division, Addition, Subtraction) to solve
7 + (-4(0)^2)
7 + (-4(0))
7 + 0
7
If x is 0 then the expression equals 7
Hope this helped
~Just a girl in love with Shawn Mendes