The observational fact about a cepheid variable star that leads to a measurement of its distance from earth is that its period of variation is directly related to its

Amath expression is a collection of one or more terms, which are separated by the signs ( + , - , x , / ).example :   8+b8+b  or  a−3a−3in algebra, an equation is a mathematical statement with two expressions where, each expression is separated by an equal (=) sign. variables can be present on both the sides of the equality (=) sign and we use letters to denote such variables.example 1:   x=4+2x=4+2  , [here, we can observe that the variable is present only on one side of the equation].example 2:   2x+3=x+42x+3=x+4  , [here, we can observe that the variables are present on both side of the equation].

The  franco-prussian  war, a  war  that was  led by prussia a coalition of  german  states, defeated  france. the  war  was the end  of  french  hegemony in europe and resulted in a unified  germany.  i hope this !