Question

if y is directly proportional to the square of x. Given that y = 20 when x = 2. What is the value of y when x = 4​

Answer 1

Answer:

y= 40

Step-by-step explanation:

y is directly proportional to x

x= 2, y= 20

now, x= 4 y= ?

x= 2+2 = 4

y= 20+20 = 40

if x becomes double y too becomes double bcoz they are promotional to each other!

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Answer 2

Step-by-step explanation:

Note -

the square of x is expressed as x²

= y ≠ x²

Make into an equation by introducing k, the constant of variation.

⇒ y = k ≠ x² = kx²

To find k, use the condition given x = 2 when y = 20

y = kx² = k = y upon x² = 20 upon 4 = 5

thus y = 5x²