Question

4. Show that a, b, c, d are in proportion if
(ii) (a+b+c+d) (a - b-c+d) = (a +b-c-d)
(a-b+c-d).​

Answer 1

Step-by-step explanation:

a^2-ab-ac+a+ab-b^2-bc+bd+ac-bc-c^2+cd+ad-b-c+d^2

=a^2ab+ac-ad+ab-b^2+bc-bd-ac+bc-c^2+cd-ad+bd-c+d^2

-2a +2a+2ad-2bd-2bc+2bd+2ac-2bc

4ad=4bc

ad=bc

hence a:b::c:d