kalau bisa sama caranya ya, makasih

jawab
 a + u3 = 100
u2 + u4 = 75

a + a r²  =100 → a (1 +r²) = 100
(1+r²) = 100/a

ar + ar³  = 100
ar (1 + r²) = 75
ar (100/a) = 75
100 r = 75
r = 3/4

(1 +r²)/ a= 100
a = (100)/(1+r²)
a = 100/(1 +(3/4)²)
a = 100 / (1 + 9/16)
a = 100 / (25/16)
a = 16/25 x 100
a = 16(4)
a = 64