\(\left(x-2\right)\left(x^2+2x+4\right)-\left(x^3+5\right)\)

\(=x^3-8-x^3-5\)

=-13

\(\left(x-2\right)\cdot\left(x^2+2x+4\right)-\left(x^3+5\right)\\ =x^2-8-x^3-5\\ =-13\)

4 x 5 + 10 = 20 + 10 = 30

3 x 9 – 20 = 27 – 20 = 7

a) \({x^2} + \dfrac{1}{4}{x^2} - 5{x^2} = (1 + \dfrac{1}{4} - 5){x^2} =  - \dfrac{{15}}{4}{x^2}\);

b) \({y^4} + 6{y^4} - \dfrac{2}{5}{y^4} = (1 + 6 - \dfrac{2}{5}){y^4} = \dfrac{{33}}{5}{y^4}\).

a: \(=x^2+6x+5-x^2\)

=6x+5

= 20 giờ 295 phút

= 24 giờ 55 phút

24 giờ 55 phút

=150+725-225

=875-225

=650

Lời giải:

$25.6+5.5.29-45.5=25.6+25.29-9.25$

$=25(6+29-9)=25.26=650$

phần dưới là tìm x

\(\dfrac{5x+2}{x^2-4}+\dfrac{x-5}{x-2}=\dfrac{5x+2+x^2-3x-10}{\left(x-2\right)\left(x+2\right)}\\ =\dfrac{x^2+2x-8}{\left(x-2\right)\left(x+2\right)}=\dfrac{\left(x+4\right)\left(x-2\right)}{\left(x-2\right)\left(x+2\right)}=\dfrac{x+4}{x+2}\\ \left(x+4\right)^2-\left(x+3\right)\left(x-2\right)=-13\\ \Leftrightarrow x^2+8x+16-x^2+x+6=-13\\ \Leftrightarrow9x=-13-22=-35\\ \Leftrightarrow x=-\dfrac{35}{9}\)

4kg x 9 – 28kg = 36kg – 28kg = 8kg

3 x 8 : 4 = 24 : 4 = 6

5 × 8 + 8 = 40 + 8 = 48

28 - 2 × 4 = 28 – 8 = 20