Variation - By Lisa

Direct variation or direct proportional for inverse.
Given thta y varies directly as x or x varies as y:
y [fish sign] OR y= kx; k is constant

Inverse or indirect variation
y [fish sign] 1/x
y =k/x
If y gets bigger, x gets smaller
If y gets smaller, x gets bigger

EXAMPLES

y=k/x
If x is trebled, y/3 [y=k/3x, move 3 onto other side so dat u get k/x : 3y=k/x]
If x increased by 250%, y * 2/7. [y=k/(7/2)x, move 7/2 on otha side, flip over]

y=k/x^2
x * 3, y/9
x *75%, y*16
y*9, x/3

y=1/[square root of x]
x=3^2, y=12. x=? if y=15

12=k/3
k=36
15=36/[square root of] x
[square root of]x= 36/15
x=36^2/15^2
x=1296/225=5.76