Question

(radical la 3 +5) x (radical la 3-5);
(x+2y) x (x-2y);
(3b+c) x (3b-c);
(radical la 5 - 2) x (radical la 5 +2).

Answer 1

$( \sqrt{3} + 5)( \sqrt{3} - 5) = 3 - 25 = - 22$

$(x + 2y)(x - 2y) = {x}^{2} - 4 {y}^{2}$

$(3b + c)(3b - c) = 9 {b}^{2} - {c}^{2}$

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

((Am aplicat formula de calcul prescurtat

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

))