若a² - ab = 9 ,ab - b² =6,则a² - b²=______,a² - 2ab +b²=________.最好写过程.

若a² - ab = 9 ,ab - b² =6,则a² - b²=______,a² - 2ab +b²=________.最好写过程.
若a² - ab = 9 ,ab - b² =6,则a² - b²=______,a² - 2ab +b²=________.
最好写过程.

若a² - ab = 9 ,ab - b² =6,则a² - b²=______,a² - 2ab +b²=________.最好写过程.
a² - ab = 9 ,ab - b² =6
两式相加可得a² - ab + ab - b² = a² - b² = 9 + 6 = 15
两式相减可得a² - ab - (ab - b²) = a² - 2ab +b² = 9 - 6 = 3

a² - ab = 9 ①，ab - b² =6②，两式相加，得：a² - b²=__15____，
①-②，得:a² - 2ab +b²=___3_____.

a² - ab = 9 ，ab - b² =6，两式相加得出a² - b²=15
两式相减得出a² - 2ab +b²=3