(ab+cd)^2 = (a^2+c^2) (b^2+d^2) prove that a/b = c/d
Answers
Answer:
Step-by-step explanation:
(ab+cd)^2 = (a^2+c^2) (b^2+d^2)
=> a^2b^2 + 2abcd + c^2d^2 = a^2b^2 + b^2c^2 + a^2d^2 + c^2d^2
=> 2abcd = b^2c^2 + a^2d^2
=> b^2c^2 + a^2d^2 - 2abcd = 0
=> (bc - ad)^2 = 0
=> bc - ad = 0
=> bc = ad
=> a/b = c/d ----divide by bd
Answer:
Proved below.
Step-by-step explanation:
Here,
a / b = c / d
⇒ ad = cb ...( 1 )
⇒ ( ad )^2 = ( cb )^2 ..( 2 )
Now,
⇒ ( ab + cd )^2
⇒ ( ab )^2 + ( cd )^2 + 2( ab )( cd ) { Using ( a + b )^2 = a^2 + b^2 + 2ab }
⇒ ( ab )^2 + ( cd )^2 + 2( abcd )
⇒ ( ab )^2 + ( cd )^2 + 2( ad )( cb )
⇒ ( ab )^2 + ( cd )^2 + 2( cb )( cb ) { ad = cb }
⇒ ( ab )^2 + ( cd )^2 + 2( cb )^2
⇒ ( ab )^2 + ( cd )^2 + ( cb )^2 + ( cb )^2
⇒ ( ab )^2 + ( cb )^2 + ( cd )^2 + ( ad )^2
⇒ b^2( a^2 + c^2 ) + d^2( c^2 + a^2 ) { cb = ad }
⇒ ( a^2 + c^2 )( b^2 + d^2 )
Hence,
( ab + cd )^2 = ( a^2 + c^2 )( b^2 + d^2 )