Question

If a equal to 9 - 4root5 find the value of (a - 1 /a)^2

Answer 1

Answer:

9-4root 5

a-1/a

= 9-4root5- 1/9-4root5

= 1

Answer 2

Answer:

320

Step-by-step explanation:

a= 9-4(root 5)

1/a=1/(9-4(root 5))

1/a=9+4(root 5)                       ....(rationalising the denominator)

(a-1/a)^2=(9-4(root 5)-(9+4(root 5)))^2

(a-1/a)^2=(9-4(root 5)-9-4(root 5))^2

(a-1/a)^2=(-8(root 5))^2                      ...(9-9=0,-4 root 5-4 root 5=-8 root 5)

(a-1/a)^2=320