Question

produsul a două nr nat este 20,iar suma lor este 9 .Aflati diferența nr

Answer 1

a+b=9
ab=20
(a+b)²=9²
a²+2ab+b²=81
a²+b²=81-2ab=81-2*20=81-40=41
(a-b)²=a²-2ab+b²=41-2*20=41-40=1
a-b=-1 sau a-b=1

Answer 2

xy=20 si x+y=9
 
x=9-y                  x=9-y
(9-y)y=20            y²-9y+20=0
                           Δ=81-80=1
                           y=4 sau y=5
x=9-4=5          sau x=9-5=4
y=4                        y=5

x-y=5-4=1   sau x-y=4-5=-1