Question

A-(3+a).(3-a). B-(xy+-5)2. C-(2x+1).(2x-1). D-(m+1).(m-1) efetue como achar melhor

Answer 1

A.
= (3 + a).(3 - a)
= 3.3 + 3.(-a) + 3.a + a.(-a)
= 9 - a²  

¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨

B.
(xy+5)²  = (xy)² + 2.5.xy + 5² = x²y² + 10xy + 25

(xy - 5)² = (xy)² - 2.5.xy + (-5)²  = x²y² - 10xy + 25

¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
C.
(2x+1).(2x - 1) = (2x)² - 1² = 4x² - 1 

¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
D.
(m + 1).(m - 1) = m² - 1² = m² - 1