Answer:
A, [tex]\sqrt{17}[/tex]
Step-by-step explanation:
a^2 + b^2 = c^2
8^2 + b^2 = 9^2
64 + b^2 = 81
b^2 = 17
b = [tex]\sqrt{17}[/tex]
by pythagoras theorem
9² = 8² + x²
x² = 81 - 64
x² = 17
x = root 17
option A
