Question

Find an expression which represents the difference when (7x+9y)(7x+9y) is subtracted from (x+5y)(x+5y) in simplest terms.

Answer 1

-48x²-116xy-56y² or

-4(12x²+29xy+14y²)

Explanation:

A.

(7x+9y)(7x+9y)=

49x²+126xy+81y²

(x+5y)(x+5y)=

x²+10xy + 25y²

subtracted from means

x²+10xy + 25y² goes first

(x²+10xy + 25y²) - (49x²+126xy+81y²)

- (49x²+126xy+81y²) means

-1 times (49x²+126xy+81y²)

-1*(49x²+126xy+81y²) = -49x²-126xy-81y²

x²+10xy+25y²-49x²-126xy-81y²

-48x²-116xy-56y²

or

B.

sometimes its good to use real numbers

use x = 0 y = 1

(9)(9) is subtracted from (5)(5)

81-25=56