Question

Không tính kết quả hãy so sánh A với B A 2008 x 2008B 2007 x 2009

Answer 1

A = 2008 x 2008

= (2007 + 1) x 2008

= 2007 x 2008 + 2008 x 1

= 2007 x 2008 + 2008

B = 2007 x 2009

= 2007 x (2008 +1)

= 2007 x 2008 + 2007 x 1

= 2007 x 2008 + 2007

Vì 2008 < 2007 => A > B

Answer 2

Ta có \(B=2007\times2009\)\(=\left(2008-1\right)\times\left(2008+1\right)\)\(=2008\times2008+2008-2008-1\)\(=2008\times2008-1\)

Vì \(-1< 0\)nên \(2008\times2008-1< 2008\times2008\)hay \(B< A\)

Answer 3

\(A=2008\times2008=2008^2\)

\(B=2007\times2009=\left(2008-1\right)\left(2008+1\right)=2008^2-1\)

\(\Rightarrow A>B\)