Question

Se x+y=4 e x-y= 10, quanto será x*2-y*2?

Answer 1

x+y=4
x-y=10

x=10+y
x=10+(-3)
x=7

10+y+y=4
2y=4-10
2y=-6
y=-3


x*2-y*2
7*2-(-3)*2
14-(-6)
14+6
20