iteracom

the first equation does not go to be the 2nd one.

they are two separate views of GDP.

The 2nd part comes from

C+S+T = C+I+G+X-M
or
C cancels
(S-I)+(T-G) = (X-M)

T-G = Govt Sector
Taxes (Govt Collection)- Govt Spending = Govt Sector

S (Savings) - I(Investment) = Private Sector.

CP