The problem
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I don't understand why the sign changed at the end?
Answer provided by our tutors
First we find the roots of the equation:
v^2+4v+3 = 0
v1 = -1
v2 = -3
We need them to graph the parabolic function:
y = v^2+4v+3
From the graph we can read what values of 'v' make that function positive, that is y >=0.
So, the solutions is (-~, -3] U [-1, +~), that is:
x <= -3, x >= -1
