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If I=∫x4+x2+1x2−x+1dx=αx+βx2+γx3+δI = \int \frac{x^4 + x^2 + 1}{x^2 - x + 1} dx = \alpha x + \beta x^2 + \gamma x^3 + \delta, δ\delta is constant of integration, then (α+2β+3γ)(\alpha + 2\beta + 3\gamma) equals

Solution

✅ Correct Option: 4

The numerator has degree 4 and the denominator has degree 2. Polynomial long division is needed to simplify before integrating.

Dividing (x4+x2+1)(x^4 + x^2 + 1) by (x2−x+1)(x^2 - x + 1):

First term: x4÷x2=x2x^4 ÷ x^2 = x^2

x2(x2−x+1)=x4−x3+x2x^2(x^2 - x + 1) = x^4 - x^3 + x^2

(x4+x2+1)−(x4−x3+x2)=x3+1(x^4 + x^2 + 1) - (x^4 - x^3 + x^2) = x^3 + 1

Second term: x3÷x2=xx^3 ÷ x^2 = x

x(x2−x+1)=x3−x2+xx(x^2 - x + 1) = x^3 - x^2 + x

(x3+1)−(x3−x2+x)=x2−x+1(x^3 + 1) - (x^3 - x^2 + x) = x^2 - x + 1

Third term: x2÷x2=1x^2 ÷ x^2 = 1

1(x2−x+1)=x2−x+11(x^2 - x + 1) = x^2 - x + 1

(x2−x+1)−(x2−x+1)=0(x^2 - x + 1) - (x^2 - x + 1) = 0

Therefore:

x4+x2+1x2−x+1=x2+x+1\frac{x^4 + x^2 + 1}{x^2 - x + 1} = x^2 + x + 1


I=∫(x2+x+1)dxI = \int (x^2 + x + 1) dx

I=x33+x22+x+δI = \frac{x^3}{3} + \frac{x^2}{2} + x + \delta


The result can be written as:

I=x+12x2+13x3+δI = x + \frac{1}{2}x^2 + \frac{1}{3}x^3 + \delta

Comparing with I=αx+βx2+γx3+δI = \alpha x + \beta x^2 + \gamma x^3 + \delta:

α=1\alpha = 1

β=12\beta = \frac{1}{2}

γ=13\gamma = \frac{1}{3}


α+2β+3γ=1+2(12)+3(13)\alpha + 2\beta + 3\gamma = 1 + 2\left(\frac{1}{2}\right) + 3\left(\frac{1}{3}\right)

=1+1+1= 1 + 1 + 1

=3= 3

Therefore, (α+2β+3γ)=3(\alpha + 2\beta + 3\gamma) = 3

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