Question

Simplify the expression 5x − (3x^2 + 9x).

Answer 1

First, you have to write the expression without the brackets.
To see what it will be, you can consider the "-" as "-1*":

\(5x-(3x^2+9x)=5x-1\cdot(3x^2+9x)\).

Now you can use the distributive property: a(b+c)=ab+ac to get rid of the brackets.
So, multiply -1 with both the numbers 3x² and 9x.