Question Details

The area bounded by the curve y = x² – 1 and the straight line x + y = 3 is

Options

A

92 sq. units

B

17√17/6 sq. units

C

4 sq. units

D

7√17/6 sq. units

Correct Answer :

17√17/6 sq. units

Solution :

The correct option is 17√17/6 sq. units.

To find the area bounded by the curve y=x2-1 and the straight line x+y=3, we first need to determine their points of intersection by setting their equations equal to each other.

From the equation of the line, we can express y in terms of x:
y=3-x

Now, equating the two expressions for y:
x2-1=3-x

Rearranging this into a standard quadratic equation form:
x2+x-4=0

We can find the roots of this quadratic equation using the quadratic formula, x=-b±b2-4ac2a, where a=1, b=1, and c=-4:
x=-1±12-4(1)(-4)2(1)=-1±1+162=-1±172

Let the two intersection points have x-coordinates:
α=-1-172 and β=-1+172

The bounded area is located between these limits. In this interval, the straight line y=3-x lies above the parabola y=x2-1. Therefore, the area A is given by the definite integral:
A=αβ(3-x)-(x2-1)dx=αβ(4-x-x2)dx

Integrating the terms:
A=4x-x22-x33αβ

Evaluating this expression yields:
A=4(β-α)-β2-α22-β3-α33

We can simplify this using algebraic relations of the roots α and β of the equation x2+x-4=0:
α+β=-1
β-α=17

Let's find the values of the components:
β2-α2=(β-α)(β+α)=(17)(-1)=-17

For the cubic difference term:
β3-α3=(β-α)(α2+αβ+β2)=(β-α)(α+β)2-αβ

Since the product of the roots is αβ=-4:
β3-α3=17(-1)2-(-4)=17(1+4)=517

Substitute these values back into the area equation:
A=417--172-5173

Now, factor out 17 and find a common denominator of 6:
A=174+12-53=1724+3-106=17176

Thus, the area bounded by the curves is 17176 square units.

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