Obs. Se aplică formulele de calcul prescurtat.
1. Prima variantă trimisă.
( a+ b+ 1)² - ( a - b)² - 2( a+ b)=
( a+ b+ 1)( a+ b+ 1)- [( a- b)( a- b)] - ( 2a+ 2b)=
( a²+ ab+ a+ ab+ b²+ b+ a+ b+ 1) -(a²- ab- ab+ b²) -2a-2b=
( a²+ b²+ 2ab+ 2a+ 2b+ 1)-( a²- 2ab+ b²) - 2a- 2b=
a²+ b²+ 2ab+ 2a+ 2b+ 1- a²+ 2ab- b² - 2a- 2b=
4ab+ 1
2. A doua variantă trimisă.
( a+ b+ 1)² - ( a + b)² - 2( a+ b)=
( a+ b+ 1)( a+ b+ 1)- [( a+ b)( a+ b)] - ( 2a+ 2b)=
( a²+ ab+ a+ ab+ b²+ b+ a+ b+ 1) -(a²+ ab+ ab+ b²) -2a-2b=
( a²+ b²+ 2ab+ 2a+ 2b+ 1)-( a²+ 2ab+ b²) - 2a- 2b=
a²+ b²+ 2ab+ 2a+ 2b+ 1- a²- 2ab- b² - 2a- 2b=
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1