SOLUTION: The variable of z varies jointly with x and y. Also, z=120 when x=-5 and y=-2. Write an equation that relates x, y and z. Then find z when x=-5 and y = -4. Equation of z = value of

SOLUTION: The variable of z varies jointly with x and y. Also, z=120 when x=-5 and y=-2. Write an equation that relates x, y and z. Then find z when x=-5 and y = -4. Equation of z = value of

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Question 291768: The variable of z varies jointly with x and y. Also, z=120 when x=-5 and y=-2. Write an equation that relates x, y and z. Then find z when x=-5 and y = -4. Equation of z = value of z =
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
Your problem didn't say whether it varies directly or inversely.
I will assume directly
z=kxy
120=k*(-5)*(-2)
120=10k
k=12
z=12xy
z=12*(-5)*(-4)
z=12*20
z=240

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