✨ Best Answer ✨
(11) (x−y−5)(x−y+2)=(x−y)²−3(x−y)−10=x²−2xy+y²−3x+3y−10
(12) (a+3b−c)²=a²+9b²+c²+6ab−2ac−6bc
(13) (x+y−7)(x+y+7)=(x+y)²−49=x²+2xy+y²−49
(14) (a+3b−2)(a−3b+2)=(a+(3b−2))(a−(3b−2))=a²−(9b²−12b+4)=a²−9b²+12b−4
(15) 2(x+2)(x−6)−(x−4)²=2(x²+4x−12)−(x²−8x+16)=2x²+8x−24−x²+8x−16=x²+16x−40
(16) (x+11)(x-11)−(x−3y)²=x²−121−(x²−6xy+9y²)=x²−121−x²+6xy−9y²=6xy−9y²−121
間違っていたらすみません…
ありがとうございます!