How where charbonneau and sacagwea useful to the group

Charbonneau bought land from Clark and briefly took up farming. He gave it up after a few months, selling the land back to Clark for 100 dollars. He also left Sacagawea and his two sons Toussaint and Jean Baptiste in Clark's protection. Sacagawea was of the Lemhi Shoshone tribe, located in the modern-day state of Idaho. … Sacagawea proved to be an invaluable resource on the expedition. She served as translator because she knew the native languages, which helped her negotiate trades with local tribes and explain that her group had come in peace

K(x) = (1/4)^x

(1,4) when x = 1, k(1) = (1/4)^1 = 1/4FALSE
(3, 1/64) when x = 3, k(3) = (1/4)^3 = 1/64TRUE
(-1,4) when x = -1, k(-1) = (1/4)^-1 = 4TRUE
(0, 1/4) when x = 0, k(0) = (1/4)^0 = 1FALSE

answer
(3, 1/64)
(-1,4)