Question

Tell whether x and y show direct variation

1. y - x = 4
2. x - y = 0
3. 8 = xy

4. What expression represents the sum of (2x-5y) and (x+y)?
5. What expression is equivalent to (7x-5) - (3x-2)?

Answer 1

i) this does not show direct variation.

ii) this shows direct variation

iii) this shows direct variation

iv) (2x-5y) + (x+y) = 3x - 4y

v) (7x-5) - (3x-2) = 4x - 3

Explanation:

i.) y - x = 4 this does not show direct variation.

ii) x - y = 0
`\Rightarrow` x = y this shows direct variation

iii) 8 = xy
`\Rightarrow` 8/x = y this shows direct variation

iv) the sum of (2x-5y) and (x+y)
`\Rightarrow` (2x-5y) + (x+y) = 3x - 4y

v) expression that is equivalent to (7x-5) - (3x-2)

`\Rightarrow` (7x-5) - (3x-2) = 4x - 5 + 2 = 4x - 3