Question

answer for the second and fourth question correct answer will be awarded brainliest

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Answer 1

Answer:

2) option C (322)

Step-by-step explanation:

Question 2:

x² = 7x - 1

=> x² - 7x  + 1 = 0

a = 1 , b = -7, c = 1

x = -b±√b²- 4ac /2a = 7 ±√49 - 4 /2 = 7 ± 3√5/2.

If x = 7 + 3√5/2 then

1/x = 2/7 + 3√5  

     = 2(7-3√5)/(7 + 3√5)(7-3√5)

      = 2(7-3√5)/49-45 = (7-3√5)/2.

Similarly if x = 7 - 3√5/2 then 1/x = 7 + 3√5/2

Now x³ + 1/x³ = (x + 1/x)³ - 3(x+1/x)

                       = [7 + 3√5/2 + 7 - 3√5/2]³ - 3 ( 7 + 3√5/2 + 7 - 3√5/2)

                        = (7)³ - 3 (7)

                         = 343 - 21 = 322.

Question 4 i will answer separately.