Question

I don’t understand this..
will someone please help? Will mark Brainliest along with 20 points.

Answer 1

Answer:

4.  250

5.  3

Step-by-step explanation:

If f(x) varies directly with x^2

f(x)= kx^2  where k is the constant of variation

f(x) =40 when x =2

40 = k(2)^2

40 = k(4)

Divide each side by 4

40/4 = k*4/4

10 =k

f(x) = 10x^2

Now we want to find f(5) which means x=5

f(5) = 10 *5^2

     = 10(25)

    = 250

5.  If f(x) varies inversely with x

f(x) = k/x  where k is the constant of variation

Multiply each side by x

f(x) *x = k

f(x) =6 when x =4

6*4 = k

24 = k

f(x) =24/x

We want to find f(x) when x=8

f(8) = 24/8

     =3

Answer 2

Answer:

4) 250

5) 3

Step-by-step explanation:

4)

f(x) varies directly with x^2. So y = kx^2

When x = 2 , f(x) = x^2 = 2^2 = 4

but f(x) = 40 so k = 10. f(x) = kx^2 = 10 * 4 = 40

so when x = 5, f(5) = 10 * (5^2) = 10 (25) = 250

5)

f(x) varies inversely with x. When x = 4, f(x) = 6

y = k/x so k = xy

k = 4 * 6 = 24

so when x = 8, f(8) = 24/8 = 3