GWD 4-18

piqiuwawa

Q18:

Which of the following is equal to (2^k)(5^{k − 1})?

A, 2(10^{k − 1})

B. 5(10^{k − 1})

C. 10^k

D. 2(10^k )

E. 10^{2k − 1}

it seems like there is a formula..but i cannot remember it at all, 请指點一下!

Answer is A

piqiuwawa

谢谢！！！