Which equations show a direct variation between x and y when solved for y?
Choose all answers that are correct.
A -10+y=3x-10
B y=-1/8x
C y+9=9x
D y=4-1
The formula for direct variation is [tex]y=kx[/tex] where [tex]k\not=0[/tex].
[tex]-10+y=3x-10\\
y=3x \Rightarrow \text{it's a direct variation}\\\\
y=-\dfrac{1}{8}x \Rightarrow \text{it's a direct variation}\\\\
y+9=9x\\
y=9x-9 \Rightarrow \text{it's not a direct variation}\\\\
y=4-1 \\
y=3 \Rightarrow \text{it's not a direct variation}[/tex]
