Question

Срочно. Заранее спасибо

Answer 1

1) (5+b)(b-5)-b² = (b+5)(b-5)-b² = b²-25-b² = -25

2) c²+(9-c)(c+9) = c²+(9-c)(9+c) = c²+81-c² = 81

3) (1/3-z)(1/3+z)-1/9 = 1/9-z²-1/9 = -z²

4) -16/49+(4/7-d)(d+4/7) = -16/49+(4/7-d)(4/7+d) = -16/49+16/49-d² = -d²