9. Quyidagi tasdiqlarning “rost” yoki “yolg‘on” ekanini aniqlang. Tasdiq yolg‘on bo‘lsa, qarshi misol (kontrmisol) keltiring. a) Musbat son + musbat son = manfiy son; b) Manfiy son + musbat son = musbat son; d) Manfiy son − musbat son = manfiy son; e) Manfiy son − manfiy son = musbat son.

a) Yolg‘on. Qarshi misol: 1 + 1 = 2, natija musbat.

b) Yolg‘on. Qarshi misol: (−3) + 1 = −2, natija manfiy.

d) Rost: manfiy sondan musbat son ayirilganda natija manfiy bo‘ladi.

e) Yolg‘on. Qarshi misol: (−5) − (−2) = −3, natija manfiy.