Question

solve please please ​

Answer 1

first rationalize a with 2-√5
and then find the value of a² - b²
it will give (a+b)²-(a-b)²
then solve it by identity a+ b and a-b

Answer 2

Answer:

Step-by-step explanation:

a = (2 -√5) / (2 + √5)

  = (2-√5)² / (2+√5)(2-√5)

  = 4+5-4√5 / 4-5

  = 9 - 4√5 / -1

  = 4√5 - 9

b = (2+√5) / (2-√5)

  = (2+√5)² / (2-√5)(2+√5)

  = 4+5+4√5 / 4-5

  = 9 + 4√5 / -1

  = -(4√5+9)

Now,

a² - b²

= (4√5-9)² - {-(4√5+9)²

= (80+81-72√5) - (80+81+72√5)

= 161-72√5-161-72√5

= -144√5