Question

esboce os gráficos das funções

a) y = 4x+20
b) y = -x - 9
c) y = 2x+10

Answer 1

a) $y=4x+20$

$y=0 \iff 4x+20=0 \iff 4x=-20 \iff x=-5 \iff (-5,0)$ 
$x=0 \iff y=4\cdot0+20 \iff y=0+20 \iff y=20 \iff (0,20)$

b) $y=-x-9$

$y=0 \iff -x-9=0 \iff x=-9 \iff (-9,0)$
$x=0 \iff y=-0-9 \iff y=-9 \iff (0,-9)$

c) $y=2x+10$

$y=0 \iff 2x+10=0 \iff 2x=-10 \iff x=-5 \iff (-5,0)$
$x=0 \iff y=2\cdot0+10 \iff y=0+10 \iff y=10 \iff (0,10)$