Mark M. answered 07/28/17
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Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
The region lies below the line y = 5 and above the graph of y = x2 + 1.
The curves intersect when x2+1 = 5
x2 = 4 So, x = 2 or -2
Area of region = ∫(from -2 to 2)(5 - (x2+1))dx
= 2∫(from 0 o 2)(4 - x2)dx (by symmetry)
= (8x - (2/3)x3)(from 0 to 2) = 16 - 16/3 = 32/3