Answer:
y = 2.25x
Step-by-step explanation:
Given x is directly proportional to y then the equation relating them is
x = ky ← k is the constant of proportion
To find k use the condition when x = 4, y = 9 , then
4 = 9k ( divide both sides by 9 )
[tex]\frac{4}{9}[/tex] = k
x = [tex]\frac{4}{9}[/tex] y ← equation of proportion
Multiply both sides by [tex]\frac{9}{4}[/tex] to clear the fraction
[tex]\frac{9}{4}[/tex] x = y , then
y = [tex]\frac{9}{4}[/tex] x , or
y = 2.25x
