Question

if a:b=c:d, prove: (5a +7b) (5c-7d) = (5a -7b) (5c+7d)​

Answer 1

Answer:

(5a +7b) (5c-7d) = (5a -7b) (5c+7d)

Step-by-step explanation:

a:b=c:d

a/b=c/d

5a/7b=5c/7d (multiplying both side by 5/7)

(5a+7b)/(5a-7b)=(5c+7d)/(5c-7d) (applying componendo and dividendo)

(5a+7b) (5c-7d)=(5a-7b) (5c+7d) (using cross multiplication)

PROVED