①16(a-b)² - 81(a+b)²
=[4(a-b)+9(a+b)][4(a-b)-9(a+b)]
=(13a+5b)(-5a-13b)
=-(13a+5b)(5a+13b)
②2(a+b)² - 8(a-b)²
=2[(a+b)²-4(a-b)²]
=2[(a+b)+2(a-b)...
①16(a-b)² - 81(a+b)²
=[4(a-b)+9(a+b)][4(a-b)-9(a+b)]
=(13a+5b)(-5a-13b)
=-(13a+5b)(5a+13b)
②2(a+b)² - 8(a-b)²
=2[(a+b)²-4(a-b)²]
=2[(a+b)+2(a-b)...