Question

qual são as resposta destas perguntas ?

Answer 1

x + y = 40

x - y = 20

Corta o +Y com o -Y

2x = 60

x = $\frac{60}{2}$ = 30

Agora descobre o Y

30 + y = 40

y = 40 - 30

y = 10

A ) $30^{2} - 10^{2}$ = 900 - 100 = 800

B ) 30 . 10 = 300

C ) $30^{2} + 10^{2}$ = 900 + 100 = 1000

D ) $\frac{30}{10}$ = 3