Question

calcule as expressões: (a-7).(a-a)= ,(6-5x)(1-2x)  ,(-x+5)(x+2) ,-4.5y=

Answer 1

(a-7).(a-a)= (a-7).x  ==> 0 = 0 

(6-5x)(1-2x)= 6 - 12x - 5x + 10x^2==> 6 - 17x + 10x^2
 
(-x+5)(x+2)= - x^2 -2x + 5x + 10 ==> - x^2 + 3x + 10 

-4.5y= - 20y