What is the x-coordinate of the vertex of the parabola whose equation is y = 3x² + 9x?
1 answer:
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Add 1 to both sides:
In cases like this, we have to remember that a root is always positive, so we can square both sides only assuming that
Under this assumption, we square both sides and we have
The solutions to this equation are
But since we can only accept solutions greater than -1, we discard and accept
.
In fact, we have
and
which is the only solution.