Sagot :
[tex]89\cdot 69\\ \\ =\left( 90-1 \right) \left( 70-1 \right) \\ \\ =90\cdot 70-90-70+1[/tex]
[tex]\\ \\ =6,300-160+1\\ \\ =6,140+1\\ \\ =6,141[/tex]
[tex]\\ \\ =6,300-160+1\\ \\ =6,140+1\\ \\ =6,141[/tex]