Suppose c and d vary inversely, and d=2 when c=17. a. Write an equation that models the variation.
b. Find d when c=68.

a. x - cd = 0

b. d = 1 / 2

Step-by-step explanation:

d = 2

c = 7

a.

c is inversely proportional to d,

c ∝ 1 / d

This inversely proportional need to be removed by using a variation / variable.

Let the variable be " x ".

c = x / d

Multiply d on both sides,

cd = x

x = cd

Subtract cd on both sides,

x - cd = 0

Hence, the equation is " x - cd = 0 ".

b.

By using the equation,

x - cd = 0

Add cd on both sides,

x = cd

c = 17, d = 2

x = 17 * 2

x = 34

To find d, when c = 68.

x = cd

34 = 68 * d

Divide 68 on both sides,

34 / 68 = d

1 / 2 = d

d = 1 / 2

step-by-step :

see explanation

step-by-step explanation:

a

(6r + 7) + (13 + 7r) ( remove brackets and collect like terms )

= 6r + 7 + 13 + 7r

= 13r + 20

b

remove brackets and collect like terms

13 - r - 1 + r

= 12 - r

c

remove brackets and collect like terms

= - 8 - r + 2r - 4

= - 12 + r

d

remove brackets and collect like terms

= 7r - - - 6r

[-   - = - - = - ]

= r -