Question

Determine as coordendas do ponto de interseção do eixo X e do eixo Y com as seguintes retas.
a) y=3x-1
b) y=2x-1
c) y=-x
d) x+y=5
e) 4y+4x=12
f) y=3x-2

Answer 1

a) y=3x-1
x= 0 ==> y = 3.0 - 1 ==> y = - 1
y=0 ==> 3x - 1 = 0 ==> 3x=1 ==> x = 1/3

b) y=2x-1
x= 0 ==> y = 2.0 - 1 ==> y = - 1
y=0 ==> 2x - 1 = 0 ==> 2x=1 ==> x = 1/2

c) y=-x
x= 0 ==> y = 0
y= 0 ==> x = 0

d) x+y=5 ==> y = - x + 5
x= 0 ==> y = - 1.0 + 5 ==> y = 5
y=0 ==> - x + 5 = 0 ==> -x= - 5(-1) ==> x = 5

e) 4y+4x=12(:4) ==> y + x = 3 ==> y = - x + 3
x= 0 ==> y = - 1.0 + 3 ==> y = 3
y=0 ==> - x + 3 = 0 ==> -x= - 3(-1) ==> x = 3

f) y=3x-2
x= 0 ==> y = 3.0 - 2  ==> y = - 2
y=0 ==>  3x - 2 = 0 ==> 3x= 2 ==> x = 2/3