Question

1) daca a-b=5 si a la a doua -b la adoua =420 aflati valoarea sumei a+b
2)

Answer 1

a-b=5
a²-b²=420
a²-b²=(a-b)(a+b)=5(a+b)=5a+5b
5a+5b=420
a+b=420/5
a+b=84

Answer 2

a-b=5 si a la doau  - b la a doua= 420=>(a+b)x(a-b)=420,dar a-b =5 deci 
(a+b)x5=420=> a+b=420:5=>a+b=84