Answers

2014-10-16T21:05:51+08:00
(12x + 7y)(15x - 7y) = 180x² - 84xy + 105xy - 49y²
                             = 180x² + 21xy - 49y²
(-25x² - 19xy + 37y²) - (180x² + 21xy - 49y²)
=  -25x² - 19xy + 37y² - 180x² - 21xy + 49y²
=  -205x² - 40xy +86y²
1 5 1
thank you very much
yw
can you answer my third question?pls.