tìm 2 số lẻ liên tiếp biết hiệu b của phương của chúng bằng 56
hsdllhvbweiuuuuuuuuuuuuuuuuuuuuuuuuuu
a)20112-2010.2012
=(2010+1)2-2010.(2010+2)
=20102+2.2010+1-20102-2.2010
=1
cau thu 2 co so ''ba'' ma so ''ba'' cua mk liet nen k the lam dc
lam tat nha
=79+75+.....+''ba''
=''ba''8.82
=''ba''116
\(2011^2-2010.2012\)
\(=2011.2011-2010.2012\)
\(=\left(2010+1\right).2011-2010.\left(2011+1\right)\)
\(=\left(2010.2011+2011\right)-\left(2010.2011+2010\right)\)
\(=2010.2011+2011-2010.2011-2010\)
\(=1\)
\(40^2-39^2+38^2-37^2+...+2^2-1^2\)
\(=\left(40^2-39^2\right)+\left(38^2-37^2\right)+...+\left(2^2-1^2\right)\)
\(=\left(40+39\right).\left(40-39\right)+\left(38+37\right).\left(38-37\right)+...+\left(2+1\right).\left(2-1\right)\)
\(=40+39+38+37+...+2+1\)
\(=\left(40+1\right).40:2\)
\(=41.20\)
\(=820\)
Ủng hộ mk nha ^-^
