Answer:
1. 
2. 
Step-by-step explanation:
Given
Variation: inverse Proportion
y = 7, x = 9
Required
- Write an equation connecting y and x
- Find y when x = 21
Given that thee variation is inversely proportional;
This implies that

Convert variation to equation
----------- Equation 1
Where k is the constant of variation
Substitute 7 for y and 9 for x in equation 1

Multiply both sides by 9


Substitute 63 for k in equation 1

Multiply both sides by x


Hence, the equation connecting x and y is 
Solving for when x = 21
Substitute 21 for x in the above equation

Divide both sides by 21


There are 12 inches in one foot. 120 x 12 = 1,440 inches. The correct ratio to be placed is the 5th one (aka 12 inches over 1 foot).
Answer:
it means that the roots of the quadratic equation is real and distinct and that means that 40 is a positive value
Answer:
22.5
Step-by-step explanation:
y=kx
20=k15
k=1•33
30=1•33x
x=22•5
Answer:
0.
Step-by-step explanation:
1) y'=(x⁴)'=4x³;
2) ∡ y'=0, ⇒ 4x³=0; ⇒ x=0.