b. ( - x² / y⁴ ) ( - y² / x⁴ ) = ( x²· y² ) / ( y⁴ ·x⁴ ) =
= ( x²·y² ) / ( x²·y²)· (x²·y²)
( - ) ( -) = +
= 1 / ( x²y²) B
c. 3· ( 2x + y) = 2· ( 3x - y)
6·x + 3·y = 6·x - 2y
6 ·x + 3·y - 6·x + 2·y = 0
5 ·y = 0 ⇒ y = 0 C
d. x = a · ( a + 1 )
z = ( a - 1 ) ·( a +1 )
x · y / z = a · ( a + 1) · ( a -1) / ( a + 1) · ( a - 1)
simplificam
= a B
