SSC CGL Model Paper 4

Question : 62 of 100

Marks: +1, -0

If a + b = 1 and ab = -6 , then whatis the value of

a_3 + b_3\ ?

Solution:

(a + b) = 1, ab = 6

⇒

(a + b)^2 = a^2 + b^2 + 1a b

⇒

( 1)^ 2 = a^2 + b^2 + 2 (-6 )

⇒

a^2 + b^2 =1 + 12 =13

⇒

a^3 + b^3 = (a+ b)(a^2 + b^2 -a b )

1 × (13 + 6) = 19

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