Answer:
1.320 ,
2.322
Step-by-step explanation:
1. Given that,
a+1/a=18
now,
(a- 1/a)² =( a+1/a)² - 4a. 1/a [(a- b)² =( a+b)² - 4a. b ]
=18² - 4 . 1 [as, a . 1/a =1 ]
=324 - 4
=320
2.Given that,
a - 1/a=4
now,
a⁴+(1/a)⁴
=(a²)² + (1/a²)² [a⁴=(a²)² & (1/a)⁴=(1/a²)²]
=(a²+1/a²) ²- 2 a². (1/a²) [a²+b²=(a+b)²-2ab]
=[(a - 1/a)² +2.a. 1/a]² - 2 [a²+b²=(a-b)²+2ab]
=[4²+2]² -2
=[16+2]²-2
=18²-2
=324-2
=322
