Question

given ,. a+b=9,. ab=18,. Find the value of (a-b)​

Answer 1

given: a + b = 9; ab = 18

to find: a - b = ?

solⁿ:

a + b = 9 ... (given a + b = 9)

(a + b)² = (9)²

a² + b² + 2ab = 81

a² + b² + 2(18) = 81 ... (given ab = 18)

a² + b² + 36 = 81

a² + b² = 45 ... (i)

now,

(a - b)² = a² + b² - 2ab

= 45 - 2(18) ... (from (i) and given)

= 45 - 36

(a - b)² = 9

a - b = 3