Answer
x = 7
or
x=6
Work Step by Step
$(x+1)^{2}$ - 15(x+1) + 56 = 0
Substitute y = x+1
$y^{2}$ - 15y +56 = 0
(y-8)(y-7) = 0
y = 8 or 7
Since x+1 = 8 or x+1 = 7
x = 7 or 6
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