Question

S = 2. 10 + 2. 12 + 2. 14 + … + 2. 20

S O S

Answer 1

đề bài đâu

Answer 2

\(S=2.10+2.12+2.14+.....+2.20\)

\(S=2.\left(10+12+14+......+20\right)\)

\(S=2.\left\{\left(10+20\right).\left[\left(20-10\right):2+1\right]\right\}\)

\(S=2.90\)

\(S=180\)

Answer 3

xong r

ko nhớ cách tính