Question

2) Efectuar: (3x – 5)(2x + 9) + (7 – 5x)(2x - 4)

Answer 1

(6×-45) (2 ×+9 ) + (7 - 5× ) (2× - 4)
(6×-45) (9× + 14×) + (14+ 20×)
(54× - 630) + (14 +20 ×)
(-576) + (34×)
542

Answer 2

Aplicas ley de los signos
(+)(+)=+
(+)(-)=-
(-)(-)=+
(-)(+)=-
y al final agrupas terminos semejantes
$(3x - 5)(2x + 9) + (7 - 5x)(2x - 4)\\ 6 {x}^{2} + 27x - 10x - 45 + 14x - 28 - 10 {x}^{2} + 20x \\ - 4 {x}^{2} + 51x - 73$