Q. Find the geometric location of the points of the process x2+2y2+3z2+xy+2xz+4yz=8 where the tangent plane is parallel to the xy plane.
Identify Equation & Condition: Identify the given equation and the condition for the tangent plane.The equation is x2+2y2+3z2+xy+2xz+4yz=8. The tangent plane must be parallel to the xy-plane, which implies the normal to the tangent plane has no z-component, i.e., ∂z∂f=0.
Calculate Partial Derivative: Calculate the partial derivative of the equation with respect to z.Differentiating x2+2y2+3z2+xy+2xz+4yz with respect to z gives 6z+2x+4y.
Set Equal & Solve for z: Set the partial derivative equal to zero to find z in terms of x and y.6z+2x+4y=0 leads to z=−31(2x+4y).
Substitute z into Equation: Substitute z back into the original equation to find the relationship between x and y.Substituting z=−31(2x+4y) into the original equation, we get:x2+2y2+3(−31(2x+4y))2+xy+2x(−31(2x+4y))+4y(−31(2x+4y))=8
Simplify Relationship between x and y: Simplify the equation to find a relationship between x and y.Expanding and simplifying, we get:x2+2y2+34(x+2y)2−32x(2x+4y)−34y(2x+4y)=8This simplifies to:x2+2y2+34(x2+4xy+4y2)−34x2−38xy−316y2=8
More problems from Pascal's triangle and the Binomial Theorem