mohon bantuannya yaah please

Kelas 8 Matematika
Bab Barisan dan Deret Bilangan

r = ⁵⁻³√(U5/U3)
r = ²√(54/6)
r = √9
r = +- 3
r = -3

U7 = U5 . r²
U7 = 54 . (-3)²
U7 = 54 . 9
U7 = 486