Answer:
If AB and CD are perpendicular, (slope of AB) x (slope of CD) = -1
9/a = -1
a = -9
Answer:
answer in the picture
Step-by-step explanation:
Answer:
see explanation
Step-by-step explanation:
given 
To rationalise multiply the numerator/denominator by the conjugate of the denominator
the conjugate of 3 + 7i is 3 - 7i, hence

distribute the numerator/denominator
=
[ note that i² = - 1 ]
= 
= 
=
+
i
=
+
i ← in standard form