Help me answer this question please (use full working)

Step-by-step explanation:

The above variation is written as

y = kx²

where k is the constant of variation

when y = 20 and x = 1

we have

20 = k(1)²

k = 20

So the formula for the variation is

y = 20x²

when x is doubled that's x = 2

y = 20(2)²

y = 20(4)

when y = 80

We have

80 = 20x

Divide both sides by 20

Hope this helps you

take the logarithm of both sides (the base of the log doesn't matter):

apply the exponent property - this says that :

distribute the log terms on both sides:

group like terms together:

divide through both sides by the coefficient on :

you can do some additional rewriting here using the properties of the logarithm to simplify things if you like: