Answer:
-3
Explanation:
You want the graphical solution to x² +6x +9 = 0.
Graph
The graph of the expression on the left shows it has a value of 0 when x = -3.
The solution is x = -3.
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Additional comment
A graphing calculator is very helpful when you want a graphical solution.
If you want to graph this by hand, you can rewrite it as ...
(x +3)² = 0
The graph of (x +3)² is a graph of the parent function y = x² after it has been shifted left 3 units. The graph will go through points (-5, 4), (-4, 1), (-3, 0), (-2, 1), (-1, 4). Of course the point at (-3, 0) indicates the solution is x=-3.