Question

Study the example below for the product of conjugate pairs (3 + sqrt(7))(3 - sqrt(7)) =9-3 sqrt 7 +3 sqrt 7 -7 =9-7 =2 Now, find the product (2 + sqrt(5))(2 - sqrt(5)) The product is

Answer 1

Answer:

- 1

Step-by-step explanation:

we need to know that

( a + b ) × ( a - b ) = $a^{2} -b^{2}$

proof :

( a + b ) × ( a - b )

$=a * a - a * b + a * b - b * b\\ = a * a - b * b\\= a^{2} - b^{2}$

so the ans is :

$=2^{2} -(\sqrt{5} )^{2} \\=4 - 5\\=-1$