Question

(11xy+4y)²-(11xy-4y)²=176xy²​

Answer 1

Answer:

=(11xy)^2+(4y)^2+2×11xy×4y -(1

1xy)^2-(4y)^2+2×11xy×4y

=88xy^2+88xy^2

=176xy^2

Answer 2

(11xy+4y)² - (11xy-4y)² = 176xy²

identity : (a+b) = a² + 2ab + b² and (a-b)² = a² - 2ab +b²

({11xy)² + 2(11xy)(4y) + (4y)²} - {(11xy)² - 2(11xy)(4y) + (4y)²} = 176xy²

(121x²y² + 88xy² + 16y²) - (121x²y² - 88xy² + 16y²) = 176xy²

121x²y²+88xy²+16y²-121x²y²+88xy²-16y² = 176xy² (when I remove the brackets the signs all change, it's like multiplying  minus with all the signs, so minus multiplied with minus becomes plus and minus multiplied with plus gives minus as it's different signs)

88xy²+88xy² = 176xy²

176xy² = 176xy²

LHS = RHS

HENCE,

(11xy+4y)²-(11xy-4y)²=176xy²