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Question

If 27(x + y) 3+ (x - y) 3= 2(2x + y) (Ax 2+ Bxy + Cy 2), then what is the value of (A - B + C)?

This question was previously asked in
SSC Selection Post 2019 Graduation Level Question Paper (16 Oct, 2019) (Shift 3)
The correct answer is

4

The correct answer is 4.

One powerful way to verify if an equation is an identity and to find unknown coefficients is by comparing the coefficients of like terms after expanding and simplifying both sides into a standard polynomial form. If the coefficients of each corresponding term (e.g., x^3, x^2y, xy^2, y^3, constants) on the left side match those on the right side, the equation is an identity, and the values of the unknown coefficients are determined. This method relies on the fact that a polynomial in multiple variables can be uniquely represented in a standard form.

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Similar Questions

  1. If a - b = 10 and ab = 4, then the value of a3- b3 + 4(a + b)2 is:

  2. If \(\rm \left(x^2+\frac{1}{x^2}\right)=18 \) and x > 1, what is the value of \(\rm \left(x^3-\frac{1}{x^3}\right)\)?

  3. If \(\sqrt 5 \) = 2.24, then find the value of \(\sqrt {\frac{{\sqrt {5 }-1 }}{{\sqrt {5 }+1 }}} \) .

  4. If x > 1, and \(\rm x^2+\frac{1}{x^2}=2\sqrt5\), what is the value of \(\rm x^4-\frac{1}{x^4}\)?

  5. If a + b = \(\frac{3}{4}\) and ab = \(\frac{1}{8}\) , then the value of a 4+ b 4+ ab 3+ ba 3is:

  6. If ab + bc + ca = 0, then find the value of \(\rm \frac{1}{a^2-b c}+\frac{1}{b^2-c a}+\frac{1}{c^2-a b}\).

  7. What would be the value of x to make 37.68 × 37.68 + 37.68 × x × x + 0.32 × 0.32 to be a perfect square?

  8. Find the square root of \(49{x^4} - \frac{{7{x^3}}}{2} + \frac{{673{x^2}}}{{16}} - \frac{{3x}}{2} + 9\)

  9. Simplify the following product:

    \(\left( {x + \frac{1}{x}} \right)\left( {x - \frac{1}{x}} \right)\left( {{x^2} + \frac{1}{{{x^2}}}} \right)\)

  10. If a + b + c = 8 and ab + bc + ca = 11, then what is the value of a 3+ b 3+ c 3- 3abc?


Important Questions from Identities

  1. If \(2x + { {1} \over 3x}= 5, x ≠ 0\) , then what is the value of  \(27x^3+{{1} \over 8x^3}\) ?

  2. If x 2 + 4y 2 = 40, xy = 6 and x > 2y then the value of x - 2y is:

  3. \(\dfrac{(5.17-2.19)^2-(5.17+2.19)^2}{11.3223}\)
  4. If a(a + b + c) 2= 1792; b(a + b + c) 2= 1536; c(a + b + c) 2= 768 then what will be the value of a?

  5. If a + b + c = 5, a 2+ b 2+ c 2= 27, a 3 + b 3 + c 3 = 125, then the value of  \(\frac{abc}{5}\)  is: 

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