Why do many historians believe the aryans migrated from central asia to the indian subcontinent

The Aryans spoke Sanskrit, which is more similar to the European languages rather than the Dravidian languages spoken in India before the Aryans invaded. Because of these similarities to the European languages, it was suggested that the Aryans came through Hindu-Kush which is now known as Afghanistan.  

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].