The value of y varies jointly with the values of x and z. when x = 4 and z = 16, the value of y is 320. when x = 8 and z = 10, the value of y is?

When x is doubled, y is doubled. When z is multiplied by 5/8, so is y. The result of both changes is that y is multplied by 2·(5/8) = 5/4. The new value of y is

... y = 5/4·320 = 400

If you really want to, you can use the formula

... y = kxz

and compute the value of k as

... k = y/(xz) = 320/(4·16) = 5

Then use this formula with the new values of x and z:

... y = 5·8·10 = 400

Option B. √x + 3

Step-by-step explanation:

f(x) = (x - 3)²

We can obtain the inverse f¯¹(x) of the above expression as follow:

f(x) = (x - 3)²

Replace f(x) with

f(x) = (x - 3)²

y = (x - 3)²

Next, interchange x and y

y = (x - 3)²

x = (y - 3)²

Make y the subject

x = (y - 3)²

Take the square root of both side

√x = y - 3

Add 3 to both side

√x + 3 = y - 3 +3

√x + 3 = y

y = √x + 3

Finally, replace y with f¯¹(x)

y = √x + 3

f¯¹(x) = √x + 3