Question

c) 25 ( x + 5 )² - 9 ( x + 7 )²

Answer 1

= 25 ( x² + 10x + 25) - 9 ( x² + 14x + 49)

= 25x² + 250x + 625 - 9x² - 126x - 441

= 16x² + 124x 148

 

Answer 2

c: Ta có: \(25\left(x+5\right)^2-9\left(x+7\right)^2\)

\(=\left(5x+25-3x-21\right)\left(5x+25+3x+21\right)\)

\(=4\cdot\left(x+2\right)\cdot\left(4x+23\right)\)