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Provide Solution For R.D.Sharma Maths Class 12 Chapter 15 Tangents and Normals Exercise 15.2 Question 8 Maths Textbook Solution.

Answers (1)

ANSWER: a=2,b=-7

HINTS:

 Differentiating  the curve   to get its slope of tangent 

GIVEN:

y^{2}=ax^{3}+b \; is \: y=4x-5

SOLUTION:

Upon differentiation

\begin{aligned} &2 y\left(\frac{d y}{d x}\right)=3 a x^{2}\\ &\Rightarrow \frac{d y}{d x}=\frac{3 a x^{2}}{2 y}\\ &m(\text { tangent }) \text { at }(2,3)=2 a \end{aligned}

The equation of tangent is given by y-y_{1}=m\left ( tangent \right )\left [ x-x_{1} \right ]

Comparing the slopes of a tangent with the given equation

2a=4

a=2

(2,3) lies on the curve, these points must satisfy

3^{2}=2\times 2^{3}+b

b=-7

 

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