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Let alpha , beta be non-real roots of (x...

Let `alpha , beta` be non-real roots of `(x^(2) + x - 3) (x^(2) + x - 2) - 12 = 0 " then" alpha ^(73) + beta^(70)`= ________

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To solve the problem, we need to find the value of \( \alpha^{73} + \beta^{70} \) where \( \alpha \) and \( \beta \) are the non-real roots of the equation: \[ (x^2 + x - 3)(x^2 + x - 2) - 12 = 0 \] ### Step 1: Simplify the equation Let \( y = x^2 + x \). Then we can rewrite the equation as: \[ (y - 3)(y - 2) - 12 = 0 \] Expanding this gives: \[ y^2 - 5y + 6 - 12 = 0 \] This simplifies to: \[ y^2 - 5y - 6 = 0 \] ### Step 2: Solve for \( y \) Now, we can use the quadratic formula to find the roots of the equation \( y^2 - 5y - 6 = 0 \): \[ y = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] Here, \( a = 1, b = -5, c = -6 \): \[ y = \frac{5 \pm \sqrt{(-5)^2 - 4 \cdot 1 \cdot (-6)}}{2 \cdot 1} \] Calculating the discriminant: \[ y = \frac{5 \pm \sqrt{25 + 24}}{2} = \frac{5 \pm \sqrt{49}}{2} = \frac{5 \pm 7}{2} \] This gives us: \[ y_1 = \frac{12}{2} = 6 \quad \text{and} \quad y_2 = \frac{-2}{2} = -1 \] ### Step 3: Find \( x \) values Now we substitute back for \( y \): 1. For \( y = 6 \): \[ x^2 + x - 6 = 0 \] Factoring gives: \[ (x - 2)(x + 3) = 0 \implies x = 2 \quad \text{or} \quad x = -3 \] 2. For \( y = -1 \): \[ x^2 + x + 1 = 0 \] Using the quadratic formula: \[ x = \frac{-1 \pm \sqrt{(-1)^2 - 4 \cdot 1 \cdot 1}}{2 \cdot 1} = \frac{-1 \pm \sqrt{-3}}{2} = \frac{-1 \pm i\sqrt{3}}{2} \] Thus, the non-real roots are: \[ \alpha = \frac{-1 + i\sqrt{3}}{2}, \quad \beta = \frac{-1 - i\sqrt{3}}{2} \] ### Step 4: Recognize \( \alpha \) and \( \beta \) as cube roots of unity Notice that \( \alpha \) and \( \beta \) can be expressed in terms of the cube roots of unity: \[ \alpha = \omega, \quad \beta = \omega^2 \] where \( \omega = \frac{-1 + i\sqrt{3}}{2} \) and \( \omega^2 = \frac{-1 - i\sqrt{3}}{2} \). ### Step 5: Calculate \( \alpha^{73} + \beta^{70} \) Using properties of cube roots of unity: \[ \alpha^{73} = \omega^{73} = \omega^{73 \mod 3} = \omega^1 = \omega \] \[ \beta^{70} = (\omega^2)^{70} = \omega^{140} = \omega^{140 \mod 3} = \omega^2 \] Thus: \[ \alpha^{73} + \beta^{70} = \omega + \omega^2 \] ### Step 6: Use the property of cube roots of unity We know that: \[ 1 + \omega + \omega^2 = 0 \implies \omega + \omega^2 = -1 \] ### Final Answer Therefore, the value of \( \alpha^{73} + \beta^{70} \) is: \[ \boxed{-1} \]
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MCGROW HILL PUBLICATION-QUADRATIC EQUATIONS-Exercise ( Level 2 (Numerical answer type questions))
  1. Let alpha , beta be non-real roots of (x^(2) + x - 3) (x^(2) + x - 2) ...

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  2. Suppose alpha, beta are irrational roots of x^(5) - 5x^(4) + 9x^(3) +...

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  3. Suppose alpha, beta, gamma are roots of x^(3) + qx + r = 0 . If (al...

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  4. Suppose f(x) = (x - a) (x - b) - (1)/(2) (b - a), where a b in R . If ...

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  5. Let f(x) = (x^(2) + 4x + 1)/( x^(2) + x + 1), x inR If m le f(x) l...

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  6. If a, b gt 0, then the least value of (a^(2) - ab + b^(2))/((a + b)^(2...

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  7. Let p, q be integers and let alpha , beta be the roots of the equatio...

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  8. Let alpha , beta be roots of x^(2) + x +1 = 0, then the equation whos...

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  9. Let S = {x in R : sqrt(x^(2) + 19 x ) - sqrt(x) + sqrt(x + 19) = x + 6...

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  10. Suppose a, b in Q and 3 - sqrt(5) is a root of x^(2) + ax + b = 0 , "t...

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  11. If y = x + (1)/(x) , (x ne 0) reduces the polynomial (x^(2) -5x + 1) (...

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  12. Suppose, a, b, c in R, a gt 0. Let alpha , beta be roots of ax^(2) + b...

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  13. If the equations x^(5) + ax + 1= 0 and x^(6) + ax^(2) + 1= 0 have a c...

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  14. If 3 + 4i is a root of x^(2) + px + q = 0, where p, q in R , then (1)/...

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  15. Suppose p ne q and difference between the roots of x^(2) + 2px + q = 0...

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  16. If the equation formed by decreasing each root of ax^(2) + bx + c = 0"...

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  17. Suppose a, b, c in R, a ne 0 .If one root of ax^(2) + bx + c = 0 is th...

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  18. Let a, b be roots of x^(2) + 2x + 5 . 71 = 0. "Let" A(n) be alpha^(n) ...

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  19. Let f(x) = (x^(2) + x + 1)/(x^(2) + 3 x + 3) x x in R . Let m be the m...

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