To find the value of \( b \) in the equation \( x^2 + bx - 55 = 0 \) given that its solutions are \( -11 \) and \( 5 \), we can use Vieta's formulas. According to Vieta's formulas:
- The sum of the roots (solutions) is equal to \( -\frac{b}{a} \).
- The product of the roots is equal to \( \frac{c}{a} \).
In this case, we have:
- The sum of the roots: \( -11 + 5 = -6 \)
- The product of the roots: \( -11 \cdot 5 = -55 \)
Since \( a = 1 \) and \( c = -55 \), we can set up the equation for the sum of the roots:
\[ -(-6) = -\frac{b}{1} \]
This gives us:
\[ -6 = -b \quad \Rightarrow \quad b = 6 \]
Thus, the value of \( b \) that satisfies the condition is:
6