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    If a + b = 13 and a3+b3=559a^3+b^3=559 a3+b3=559​. Find the value of a2+b2.a^2+b^2 .a2+b2.​​
    Question

    If a + b = 13 and a3+b3=559a^3+b^3=559 ​. Find the value of a2+b2.a^2+b^2 .​​

    A.

    105

    B.

    85

    C.

    125

    D.

    95

    Correct option is B

    Given:
    a + b = 13
    a3+b3=559a^3 + b^3 = 559​​
    Formula Used:
    a3+b3=(a+b)(a2+b2ab)a^3 + b^3 = (a+b)(a^2 + b^2 - ab)​​
    (a+b)2=a2+b2+2ab(a+b)^2 = a^2 + b^2 + 2ab​​
    Solution:
    Substitute the known values into the sum of cubes formula:
    559=13(a2+b2ab)559 = 13(a^2 + b^2 - ab)​​
    a2+b2ab=55913=43a^2 + b^2 - ab = \frac{559}{13} = 43​​
    Substitute the known values into the square formula:
    132=a2+b2+2ab13^2 = a^2 + b^2 + 2ab​​
    169=a2+b2+2ab169 = a^2 + b^2 + 2ab​​
    We now have two equations:
    1)a2+b2ab a^2 + b^2 - ab​ = 43
    2)a2+b2+2ab a^2 + b^2 + 2ab​ = 169
    Subtract equation (1) from equation (2):
    3ab = 169 - 43 = 126
    ab = 42
    Substitute the value of ab back into equation (1):
    a2+b242=43a^2 + b^2 - 42 = 43​​
    a2+b2a^2 + b^2 ​= 43 + 42 = 85
    Final Answer
    So the correct answer is (b)

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