When simplifying the expression 9(21x+5x)2−18x , what is the coefficient of x after the first step?

To simplify the expression 9(21x+5x)2−18x, we need to start by combining like terms within the parentheses.

9(21x+5x)2 can be rewritten as 9(26x)2 since 21x+5x = 26x.

Therefore, the expression becomes 9(26x)2 − 18x.

The coefficient of x after the first step is 26.