2<3 | *-2
if the sign it is not changed ⇒ -4 < -6 but it is false ( the negative number is bigger when the number after is smaller)
⇒the sign must be changed
- 4 > -6
but in equation the sign remain " ="
⇒ in equation the change does not happen
Ex 3=2+1 | -2
-3*(-2)= - 6 = -2*(2+1)= - 4 - 2 true
