Question

Calcule:

a)(7+√19).(7-√19)
b)(-3√5+1).(-3√5-1)
c)(2√7+3√5)²

Answer 1

a)(7+√19).(7-√19) = 49 - 19 ==> 30

b)(-3√5+1).(-3√5-1) = + 9.5 - 1 ==> 45 -1 ==> 44 

c)(2√7+3√5)²=(2√7)²+2.(2√7+3√5)+(2√7+3√5)² ==>(4.7)+ 2.(2√7).(3√5) + (9.5)
                   ___
28 + 2.(2.3√7.5 ) + 45 ==> 73 + 12√35