Question

y varies jointly as x and z. Write the appropriate joint-variation equation, and find y for the given values of x and z.

y = -108 when x = -4 and z = 3; x = 6 and z = -2
a.
y = 9xz; -108
c.
y = -6xz; -104
b.
y = -7xz; 392
d.
y = ; 60

Answer 1

Again, joint variation means y is directly proportional to both x and z.

I.e. y = kx and y = kz, to combine = y = kxz, for some constant k.

1) Finding the constant k by solving for it simultaneously.
y = -108 when x = -4 and z = 3; x = 6 and z = -2

-108 = k (-4)(3)
k = ?
With this given k, substitute inside the below equation to find y.
y = k (6)(-2)

Answer 2

so a

Answer 3

Yes