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WAEC Further Mathematics 2022 Paper

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Question : 14

Total: 45

If

x^2+y^2+-2x-6y+5 =0

, evaluate dy/dx when x=3 and y=2.

2
-2
-4
4

Solution:

Concept:

Use implicit differentiation to find

\frac{dy}{dx}

.

Explanation:

Given:

x^2+y^2-2x-6y+5=0

.

Differentiate each term with respect to

x

:

2x+2y\frac{dy}{dx}-2-6\frac{dy}{dx}=0

.

Substitute

x=3

and

y=2

:

2(3)+2(2)\frac{dy}{dx}-2-6\frac{dy}{dx}=0

.

6+4\frac{dy}{dx}-2-6\frac{dy}{dx}=0

.

4-2\frac{dy}{dx}=0

.

-2\frac{dy}{dx}=-4

.

\frac{dy}{dx}=2

.

Answer:

\frac{dy}{dx}=2

.

Correct option: A.

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