Question

a²-4a-1=0 find the value of a²-1/a²​

Answer 1

Given :

• a² - 4a - 1=0

To find :

• a² - 1/a²

Solution :

We have,

a² - 4a - 1 = 0

a² - 1 = 4a

a² - 1/a = 4 [Dividing both sides by a]

(a - 1/a)² = 4²

a² + 1/a² - 2 = 16

a² + 1/a² = 16 + 2

a² + 1/a² = 18

Extra formula's :

• t_n = a + ( n - 1 ) d

• S_n = n/2 [ 2a + ( n - 1 ) d ]

• S_n = n/2 ( a + 1 )

• Volume of cuboid = l × b × h

• C.S.A of cuboid = 2(l + b)h

• T.S.A of cuboid = 2(lb + bh + lh)

• C.S.A of cube = 4a²

• T.S.A of cube = 6a²

• Volume of cube = a³

• Volume of sphere = 4/3πr³

• Surface area of sphere = 4πr²