Question

Evaluate 3(x+y)
- ----
4xy^2
when x = 2/3 and y=-2

Answer 1

3(2/3 -2)/4(2/3)(4)=(-4)3/32=-3/8

Answer 2

[ 3(x+y) ]/[ 4xy^2 ]


[ 3(2/3 + (-2)) ]/[ 4(2/3)(-2)^2 ]


[ 3(2/3 + (-2)) ]/[ 4(2/3)(4) ]


[ 3(2/3 + (-2)) ]/[ 32/3 ]


[ 3(2/3 - 2) ]/[ 32/3 ]


[ 3(-4/3) ]/[ 32/3 ]


[ -12/3 ]/[ 32/3 ]


(-12/3)(3/32)


-36/96


-3/8


So [ 3(x+y) ]/[ 4xy^2 ] = -3/8 when x = 2/3 and y = -2