1. Original formula = (a 2-b 2) * (-a) 2-b 2) = a 4-2a 2 * b 2+b * 4-square difference formula expansion (only fill in the last equal sign).

2.x？ -( 10xy )+25y？ =( x-5y)？

calculate

1. Original formula =12mn2-2mn2n6+1/4 * m2n6.

2. The original formula = 6Y2-11y+3+6Y2-29y+20 =12Y2-40Y+23.

3. The original formula = 4x 2+ 13x- 12.

4. Original formula = 6x 2-5xy-6y 2

-Looks like all you need to do is expand. Don't you understand? Multiply each item in the first bracket by each item in the second bracket, and don't leave it out.