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Answer 1

Step-by-step explanation:

10. 2a+7b=11, ab=2

(2a+7b)² =4a²+49b²+28ab

(11)² =4a²+49b²+28×2

121 =4a²+49b²+56

121-56 =4a²+49b²

65 =4a²+49b²

11. Given : 7x - 6y = 30

xy = 5

7x - 6y = 30

=> ( 7x - 6y )² = ( 30 )²

=> (7x)² + (6y)² - (2)(7x)(6y) = 900

=> 49x² + 36y² - 84xy = 900

=> 49x² + 36y² - 84(5) = 900

=> 49x² + 36y² - 420 = 900

=> 49x² + 36y² = 900 +420

Therefore , 49x² + 36y² = 480

12. a) a - 1/a =5

take squaring both side

(a - 1/a )^2 = (5)^2

a^2 +1/a^2 -2.a.1/a =25

a^2+1/a^2 -2 =25

a^2+1/a^2 =27

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