To solve the equation \( y^2 - 18 = -17 \), first, we can add 18 to both sides:
\[ y^2 - 18 + 18 = -17 + 18 \]
This simplifies to:
\[ y^2 = 1 \]
Next, we take the square root of both sides. Remember that taking the square root will give us both the positive and negative solutions:
\[ y = \sqrt{1} \quad \text{or} \quad y = -\sqrt{1} \]
Which gives us:
\[ y = 1 \quad \text{or} \quad y = -1 \]
Thus, the solutions for \( y \) are:
\[ y = 1 \quad \text{or} \quad y = -1 \]