Find an equation of variation where y varies jointly as x and the square of z, and where y=70, when x=21 and z=5.

Step-by-step explanation:

Given

y jointly varies to x and z^2

Required

Find the equation

We start by writing out the variation;

Write as equation

Substitute values of x,y and z

Divide both sides by 7

Substitute k in

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this

99

step-by-step explanation: