№ 25 Алгебра = № 25 Математика
Перетворіть на многочлен вираз:
1) 7b2(b – 3);
2) 4(b – 3) – 2(2b + 1);
3) (m + 2)(m – 4);
4) –2x3(4 – x2 + x);
5) 3(2c – 6) – (5c – 18);
6) (3x + y)(x – y).
Розв'язок:
1) 7b2(b – 3) = 7b2 ⋅ b − 7b2 ⋅ 3 =
= 7b3 − 21b2;
2) 4(b – 3) – 2(2b + 1) = 4b – 12 − 4b – 2 =
= −14;
3) (m + 2)(m – 4) = m2 − 4m + 2m – 8 =
= m2 − 2m − 8;
4) –2x3(4 – x2 + x) = −2x3 ⋅ 4 + 2x3 ⋅ x2 −
− 2x3 ⋅ x = −8x3 + 2x5 − 2x4;
5) 3(2c – 6) – (5c – 18) = 6c – 18 −
− 5c + 18 = c;
6) (3x + y)(x – y) = 3x ⋅ x − 3x ⋅ y + y ⋅ x –
− y ⋅ y = 3x2 − 3xy + xy − y2 =
= 3x2 − 2xy − y2.