Question

X x 2011-X =2011 x 2009-2011

Answer 1

x . 2011 - x = 2011 . 2009 - 2011

x.(2011 - 1) = 4038088

x . 2010 = 4038088

x = 4038088: 2010

x = 2008,999005

Answer 2

X x 2011-X = 2011 x 2009 - 2011

X x ( 2011-1)   = 2011 x (2009- 1)

X x 2010        = 2011 x 2010

=> X=2011

Answer 3

Tim giá trị biểu thức : A = 1/4+1/12+1/24+1/40+1/60+1/84