Answers
4 and
-12
Step-by-step explanation
The octagons can be considered congruent when their areas are the same.
That is:
48 mm² = x² + 8x mm²
x² + 8x = 48
x² + 8x + 4² = 48 + 4²
(x + 4)² = 48 + 16
= 64
x + 4 = √64 or x + 4 = -√64
x = 8 - 4 x = -8 -4
= 4 = -12