18
O‘zaro teskari sonlar
Darslik, 73–77-betlar
MaqsadO‘zaro teskari sonlar tushunchasini bilish va berilgan songa teskari sonni topish.
Yangi so‘zlar
o‘zaro teskari sonlar · reciprocal (mutually inverse) numbersteskari son · reciprocalko‘paytma 1 · product equal to 1noto‘g‘ri kasr · improper fraction
Tushuntirish
Ko‘paytmasi 1 ga teng ikki son o‘zaro teskari sonlar deyiladi. a/b kasrga teskari son b/a, chunki a/b · b/a = 1. Natural son n ga teskari son 1/n. Aralash songa teskari sonni topish uchun uni avval noto‘g‘ri kasrga aylantiramiz: 2 1/4 = 9/4, teskarisi 4/9. 0 soniga teskari son yo‘q, chunki 0 ni har qanday songa ko‘paytirsak, 0 chiqadi, 1 emas. Teskari son tushunchasi kasrlarni bo‘lish uchun kerak.
Namunalar
3/7 ga teskari son 7/3: 3/7 · 7/3 = 21/21 = 1. 5 ga teskari son 1/5.
2 1/4 = 9/4, shuning uchun teskari son 4/9. Tekshiramiz: 9/4 · 4/9 = 1.
Sinfda faoliyat
«Teskarisini top»: o‘qituvchi kartochkada kasr ko‘rsatadi, o‘quvchilar teskari sonni yozadi va sherigi bilan almashib, ko‘paytirib 1 chiqishini tekshiradi.
Mashq
1
5/8 ga teskari sonni yozing.
8/5
2
3 1/2 ga teskari sonni toping.
2/7
3
3/4 · x = 1 tenglamada x ni toping.
4/3
4
Nima uchun 0 ga teskari son yo‘q?
0 ni har qanday songa ko‘paytirsak 0 chiqadi, hech qachon 1 emas.