已知a+b=3,则a²-b²+6b的值为____.

已知a+b=3,则a²-b²+6b的值为____.
已知a+b=3,则a²-b²+6b的值为____.

已知a+b=3,则a²-b²+6b的值为____.
答：
a+b=3
a²-b²+6b
=(a+b)(a-b)+6b
=3(a-b)+6b
=3a-3b+6b
=3a+3b
=3(a+b)
=3*3
=9

a^2-b^2+6b
=(a+b)(a-b)+6b
=3(a-b)+6b
=3a-3b+6b
=3a+3b
=3（a+b)
=3*3
=9