a,chứng minh : 1/2²+1/2³+1/2⁴+.....+1/2ⁿ<1

b,cho A=2²+2³+2⁴+....+2⁶⁴. Chứng minh A chia hết cho 3,7,15

Complete the texts. Use the present simple affirmative or negative form of the verbs below.

come  - get - up - go - meet - not live - not see - play - say - study - walk

My grandfather My grandfather Albert is 86 years old. He 1.................. far from us, but we 2............. him a lot because he’s always very busy. He 3 ..................early every morning and 4............ his dog, Fifi, in the park. In the afternoon, he 5............. his friends and they 6.............. golf or he 7........... out with Adora, his new girlfriend. Adora 8....... from Spain, so every Tuesday my grandfather 9 ..............Spanish at a language school. He 10........... ‘You’re never too old to learn!’ He’s a great man!