To solve the formula \( x = \frac{-b}{2a} \) for \( a \), we need to isolate \( a \) on one side of the equation. Let us proceed step-by-step:
1. Start with the given formula:
[tex]\[
x = \frac{-b}{2a}
\][/tex]
2. Multiply both sides of the equation by \( 2a \) to get rid of the denominator on the right-hand side:
[tex]\[
2a \cdot x = -b
\][/tex]
3. Simplify the equation:
[tex]\[
2ax = -b
\][/tex]
4. To isolate \( a \), divide both sides of the equation by \( 2x \):
[tex]\[
a = \frac{-b}{2x}
\][/tex]
Thus, when the formula \( x = \frac{-b}{2a} \) is solved for \( a \), the equation is:
[tex]\[
a = \frac{-b}{2x}
\][/tex]
So the correct answer is:
[tex]\[
a = \frac{-b}{2x}
\][/tex]