Question

9 minus radical din 7,pe langa 9 plus radical din 7

Answer 1

$(9 - \sqrt{7})(9 + \sqrt{7}) = \\ \\ {9}^{2} - \sqrt{7} ^{2} = \\ \\ 81 - 7 = 74$

Answer 2

( 9 - √7 ) ( 9 + √7 ) = 9² - (√7)² = 81 - 7 = 74

→ am aplicat formula ( a - b ) ( a + b ) = a² - b²