If (x+y)^2=7x^3y^4, find dy/dx by implicit differentiation 2. Find the equation of the tangent line to 3x^2+6xy-y^2=-9 at (0,3) 3.

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1.    If (x+y)^2=7x^3y^4, find dy/dx by implicit differentiation

2.    Find the equation of the tangent line to 3x^2+6xy-y^2=-9 at (0,3)

3.    A company's sales volume y (in millions of dollars) is related to its advertising expenses x (in thousands of dollars) by 15y-20x+xy=0. Find the rate of change of the sales volume with respect to advertising expenses when its expenses is 10,000. Interpret your answer. 

Answers 1) (21X^2y^4-2x-2y)/(2x+2y-{28x^3y3})

2) y=3x+3

3) 12/25=0.48. There is an approximate increase in the sales volume of $480,000 when $11,000 is spent on advertising