Question

If (a+b)(a-b)=21,a+b=7 and a-b=3 what Is the value of a

Answer 1

9514 1404 393

Answer:

5

Explanation:

Add the latter two equations and you get ...

(a +b) +(a -b) = (7) +(3)

2a = 10 . . . . . . . . . . . . . . . simplify

a = 5 . . . . . . . divide by 2