Given that 0.8 is one root of the equation, x3 - 0.6x2 - 1.84x + 1.344 = 0. The other roots of this equation will be

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Given that 0.8 is one root of the equation,  x3 - 0.6x2 - 1.84x + 1.344 = 0. The other roots of this equation will be
1. 1.1 and - 1.4
2. - 1.2 and - 1.4
3. 1.2 and -1.4
4. -1.1 and - 1.4

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Correct Answer - Option 3 : 1.2 and -1.4

Given

Equation =  x3 - 0.6x2 - 1.84x + 1.344 = 0

One root = 0.8

Concept

If α, β and γ are roots of equation ax³ + bx² + cx + d = 0, then

α + β + γ = -b/a

αβ + βγ + γα = c/a

αβγ = - d/a

calculation

Let, α = 0.8

Hence, 0.8 + β + γ = 0.6

⇒ β + γ = - 0.2      ---- (1)

By putting values of the other two roots we can find the answer.

From option 1, β + γ =  1.1 + (-1.4) = -0.3 (Not satisfied)

From option 2, β + γ =  - 1.2 - 1.4 = -2.6 (Not satisfied)

From option 1, β + γ =  1.2 -1.4 = -0.2 (satisfied)

From option 1, β + γ =  -1.1 - 1.4 = -2.5 (Not satisfied)

Hence, option 3 is the correct answer.