189° Вправа 189Алгебра 8 клас Тарасенкова 2025 · § 5 · стор. 57

189. Спростіть вираз.

1) ${\displaystyle \frac{2}{9a^2}\cdot 18=}$${\displaystyle \frac{2\cdot 2\cdot \stackrel{1}{\cancel{9}}}{\underset{1}{\cancel{9}}{a}^2}=}$${\displaystyle \frac{4}{a^2}}$;

2) ${\displaystyle \frac{2}{7b}\cdot 28b^2=}$${\displaystyle \frac{2\cdot 4\cdot \stackrel{1}{\cancel{7}}\cancel{b}b}{\underset{1}{\cancel{7}}\cancel{b}}=}$${\displaystyle 8b}$;

3) ${\displaystyle \frac{2}{15x}\cdot (-24x^3)=}$${\displaystyle -\frac{2\cdot 8\cdot \stackrel{1}{\cancel{3}}\cancel{x}{x}^2}{\underset{5}{\cancel{15}}\cancel{x}}=}$${\displaystyle -\frac{16x^2}{5}}$;

4) ${\displaystyle (a+2)\cdot \frac{9}{2+a}=}$${\displaystyle \frac{\cancel{\left(a+2\right)}\cdot 9}{\cancel{a+2}}=}$${\displaystyle 9}$;

5) ${\displaystyle (3b-12)\cdot \frac{4}{4-b}=}$${\displaystyle \frac{3\cancel{\left(b-4\right)}\cdot 4}{-\cancel{\left(b-4\right)}}=}$${\displaystyle -12}$;

6) ${\displaystyle (a-4a^2)\cdot (-\frac{5}{4a-1})=}$${\displaystyle \frac{-a\cancel{\left(4a-1\right)}\cdot (-5)}{\cancel{4a-1}}=}$${\displaystyle 5a}$.