10^100=1000...000(có 100 chữ số 0)

1 thế kỉ=100 năm

\(\dfrac{5}{4}\)thế kỉ=\(\dfrac{5}{4}\)x100=125 năm

abxab+ab=756

abx(ab+1)=756

abx(ab+1)=27x28

⇒ab=27

65,6kg=6,56yen

2460+300.(96:8+15)

=2460+300.(12+15)

=2460+300.27

=2460+8100=10560

Ket qua:\(\dfrac{8}{15},\dfrac{3}{5},\dfrac{2}{3},\dfrac{12}{9}\)
 

\(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+...+\dfrac{1}{90}\)

=\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{9.10}\)

=\(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}\)

=\(1-\dfrac{1}{10}=\dfrac{9}{10}\)

-5,2-(4,19-3,2)+(3,81+2,5)

=-5,2-4,19+3,2+3,81+2,5

=(-5,2+3,2)-4,19+6,31

=-2+2,12

=0,12

\(\dfrac{-x+3}{6}=\dfrac{5}{2}\)

⇒2(-x+3)=5.6

⇒-2x+6=30

⇒-2x=30-6=24

⇒x=24:(-2)=-12

Vay x=-12