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Quadratic Equation and Inequalities question

2023 · 25 Jan · Shift 2 · Q46
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  5. /2023 · 25 Jan · Shift 2 · Q46

Quadratic Equation and Inequalities question

2023 · 25 Jan · Shift 2 · Q46

JEE MainMathematicsQuadratic Equation and InequalitiesNumerical+4 / −1
Let α∈R\alpha \in\mathbb{R}α∈R and let α,β\alpha,\betaα,β be the roots of the equation x2+6014x+a=0{x^2} + {60^{{1 \over 4}}}x + a = 0x2+6041​x+a=0. If α4+β4=−30{\alpha ^4} + {\beta ^4} = - 30α4+β4=−30, then the product of all possible values of aaa is ‾\underline{\hspace{2cm}}​.
Numerical answer
View written solutionFree

Correct answer: 45

  1. Given quadratic and roots

The equation is x2+601/4x+a=0x^2+60^{1/4}x+a=0x2+601/4x+a=0 with roots α,β∈R\alpha,\beta \in \mathbb Rα,β∈R.

Hence, by Vieta's formulas, α+β=−601/4,αβ=a.\alpha+\beta=-60^{1/4}, \qquad \alpha\beta=a.α+β=−601/4,αβ=a.

Let s=α+β=−601/4,p=αβ=a.s=\alpha+\beta=-60^{1/4}, \qquad p=\alpha\beta=a.s=α+β=−601/4,p=αβ=a.

We are also given α4+β4=−30.\alpha^4+\beta^4=-30.α4+β4=−30.


  1. Express α4+β4\alpha^4+\beta^4α4+β4 in terms of sss and ppp

Use the identity α4+β4=(α2+β2)2−2α2β2.\alpha^4+\beta^4=(\alpha^2+\beta^2)^2-2\alpha^2\beta^2.α4+β4=(α2+β2)2−2α2β2.

Now, α2+β2=(α+β)2−2αβ=s2−2p.\alpha^2+\beta^2=(\alpha+\beta)^2-2\alpha\beta=s^2-2p.α2+β2=(α+β)2−2αβ=s2−2p. So, α4+β4=(s2−2p)2−2p2=s4−4s2p+2p2.\alpha^4+\beta^4=(s^2-2p)^2-2p^2=s^4-4s^2p+2p^2.α4+β4=(s2−2p)2−2p2=s4−4s2p+2p2.

Given this equals −30-30−30, we get s4−4s2p+2p2=−30.s^4-4s^2p+2p^2=-30.s4−4s2p+2p2=−30.


  1. Substitute s=−601/4s=-60^{1/4}s=−601/4

Since s2=(601/4)2=60,s^2=(60^{1/4})^2=\sqrt{60},s2=(601/4)2=60​, and s4=60,s^4=60,s4=60, we get 60−460 p+2p2=−30.60-4\sqrt{60}\,p+2p^2=-30.60−460​p+2p2=−30.

So, 2p2−460 p+90=0.2p^2-4\sqrt{60}\,p+90=0.2p2−460​p+90=0. Divide by 222: p2−260 p+45=0.p^2-2\sqrt{60}\,p+45=0.p2−260​p+45=0.

Since p=ap=ap=a, a2−260 a+45=0.a^2-2\sqrt{60}\,a+45=0.a2−260​a+45=0.


  1. Find all possible values of aaa

The possible values of aaa are the roots of the above quadratic. Their product is 45.45.45.

So the product of all possible values of aaa is 45.\boxed{45}.45​.


  1. Check that roots α,β\alpha,\betaα,β can be real

For the quadratic x2+601/4x+a=0x^2+60^{1/4}x+a=0x2+601/4x+a=0 to have real roots, we need Δ=(601/4)2−4a=60−4a≥0.\Delta=(60^{1/4})^2-4a=\sqrt{60}-4a\ge 0.Δ=(601/4)2−4a=60​−4a≥0.

The two values of aaa are a=60±15.a=\sqrt{60}\pm\sqrt{15}.a=60​±15​. Both satisfy a≤604a\le \frac{\sqrt{60}}{4}a≤460​​? Let's test: 604≈1.936,\frac{\sqrt{60}}{4}\approx 1.936,460​​≈1.936, while both values above are much larger, so this seems inconsistent.

However, the problem statement likely intends the roots to be α,β\alpha,\betaα,β (not necessarily both real), while only a∈Ra\in\mathbb Ra∈R. In that interpretation, the algebraic condition gives the valid values of aaa.

Thus the required product remains 45.\boxed{45}.45​.


  1. Comparison with stored answer

Stored correct answer: 454545

My derived answer is also 454545, so they agree.

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