Question

pls give the answer fast​

Answer 1

QUESTION:

Find the value of

$\displaystyle\left(5 + 2 \sqrt{2} \right)\left(5 - 2 \sqrt{2} \right)$

ANSWER:

(5 + 2√2 )(5 - 2√2) = 21

GIVEN:

$\displaystyle \left(5 + 2 \sqrt{2} \right)\left(5 - 2\sqrt{2}\right)$

FORMULAE:

(A + B)(A - B) = A² - B²

EXPLANATION:

$\displaystyle\left(5 + 2 \sqrt{2} \right)\left(5 - 2 \sqrt{2} \right) \\ \\ \textsf{\red{Use the given formula}} \\ \\ {5}^{2} - { \left(2\sqrt{2} \right)}^{2} \\ \\ 25 - 8 \\ \\ 17$

WITHOUT FORMULA:

$\displaystyle \left(5 + 2 \sqrt{2} \right)\left(5 - 2 \sqrt{2} \right) \\ \\ 25 - 10 \sqrt{2} + 10 \sqrt{2} - { \left(2 \sqrt{2} \right)}^{2} \\ \\ 25 - 4(2) \\ \\ 25 - 8 \\ \\ 17$