Explanation:
that kind of wording is always misleading.
please give my regards and comments to your teacher.
a square root has ALWAYS 2 solutions : a positive AND a negative one.
in that sense the negative solution to a square root is NOT an extraneous solution.
only any value of x < -10 (to make the argument of the square root negative) as solution would be extraneous.
so, if your teacher wants to say that only the positive solutions of a square root are allowed, it has to be said as an extra definition or by applying the "+" sign to the square root.
so,
x + 4 = sqrt(x + 10)
since the 2 solutions are already given to us, we only need to use them in the equation and see what happens.
x = -1
-1 + 4 = sqrt(-1 + 10)
3 = sqrt(9) = 3 (actually, it is ±3)
so, x = -1 is a real solution.
x = -6
-6 + 4 = sqrt(-6 + 10)
-2 = sqrt(4) = 2 (actually, it is ±2)
so, based on your teacher's expectation of only positive results of the square root (even though it was not stated),
x = -6 is an extraneous solution.
therefore, the third answer (c) is the "correct" answer.
but actually, formally, the second answer (b) is the truly correct answer.