1.
a) x^2 - y + x - xy
= x( x+1) - y( 1 + x)
= ( x + 1) ( x - y)
b) xz + yz - 4( x + y )
= z( x + y) -4( x + y)
= ( z - 4) ( x = y)
c)
2.
a)
b) 7x( x + 2) - x - 2 = 0
7x( x + 2) -( x + 2) = 0
( x + 2) (7x - 1) = 0
Ta có: x + 2 = 0 ⇒ x = -2
7x - 1 = 0 ⇒ x = 1/7