№424
(2√5 + 1)(2√5 - 1) = (2√5)² - 1² = 4•5 - 1 = 19;
(5√7 - √13)(5√7 + √13) = (5√7)² - (√13)² = 25•7 - 13 = 175 - 13 = 162;
(3√2 - 2√3)(2√3 + 3√2) = (3√2)² - (2√3)² = 9•2 - 4•3 = 6;
(0,5√14 + √3)(√3 - 0,5√14) = (√3)² - (0,5√14)² = 3 - 0,25•14 = 3 - 3,5 = - 0,5;
(1+3√5)² = 1² + 2•1•3√5 + (3√5)² = 1+6√5+45 = 46+6√5;
(2√3-7)² = (2√3)² - 2•2√3•7+7² = 12-28√3+49 = 61-28√3;
(2√10-√2)² = 40-2•2√10•√2+2 = 42-4√20 = 42-4•2√5 = 42-8√5.
(3√6-2√3)² = (3√6)² - 2•3√6•2√3 + (2√3)² = 54 - 12√18 + 12 = 66 - 12•3√2 = 66 - 36√2.
(7+28)*2=70 см периметр