\(a,21-22+23-24=-1+\left(-1\right)=-2\\ b,125-\left(115-99\right)=125-115+99=10+99=109\)

a) 21 - 22 + 23 - 24

= (21 + 23) + (-22 - 24)

= 44 - 46

= -2

b) 125 - (115 - 99)

= 125 - 115 + 99

= 10 + 99

= 109

a, - 2

b, 109

Câu 5:

a: \(31\cdot\left(-18\right)+31\cdot\left(-81\right)-31\)

\(=31\left(-18-81-1\right)\)

\(=31\cdot\left(-100\right)=-3100\)

b: \(\left(-12\right)\cdot47+\left(-12\right)\cdot52+\left(-12\right)\)

\(=\left(-12\right)\left(47+52+1\right)\)

\(=-12\cdot100=-1200\)

c: \(13\cdot\left(23+22\right)-3\cdot\left(17+28\right)\)

\(=13\cdot45-3\cdot45\)

\(=45\cdot10=450\)

d: \(-48+48\left(-78\right)+48\left(-21\right)\)

\(=48\left(-1-78-21\right)\)

\(=48\left(-100\right)=-4800\)

Câu 4:

a: \(\left(-6-2\right)\left(-6+2\right)=\left(-8\right)\cdot\left(-4\right)=32\)

b: \(\dfrac{\left(7\cdot3-3\right)}{-6}=\dfrac{21-3}{-6}=\dfrac{18}{-6}=-3\)

c: \(\left(-5+9\right)\cdot\left(-4\right)=4\cdot\left(-4\right)=-16\)

d: \(\dfrac{72}{-6\cdot2+4}=\dfrac{72}{-12+4}=\dfrac{72}{-8}=-9\)

Bài 5:

a: x(x-4)=0

=>\(\left[{}\begin{matrix}x=0\\x-4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\)

b: Đề thiếu vế phải rồi bạn

Bài 6:

a: \(\left(-5\right)\cdot\left(-6\right)\cdot\left(-4\right)\cdot2\)

\(=-\left(2\cdot5\right)\cdot\left(4\cdot6\right)\)

\(=-24\cdot10=-240\)

b: \(\left(-3\right)\cdot2\cdot\left(-8\right)\cdot5\)

\(=3\cdot2\cdot8\cdot5\)

\(=\left(3\cdot8\right)\cdot\left(2\cdot5\right)\)

\(=24\cdot10=240\)

\(a)-\left(\frac{3}{10}-\frac{6}{11}\right)-\left(\frac{21}{30}-\frac{5}{11}\right)\)

\(=-\frac{3}{10}+\frac{6}{11}-\frac{21}{30}+\frac{5}{11}\)

\(=\left(-\frac{3}{10}-\frac{21}{30}\right)+\left(\frac{6}{11}+\frac{5}{11}\right)\)

\(=-1+1\)

\(=0\)

\(b)\left(\frac{13}{5}+\frac{7}{16}\right)-\left(\frac{11}{16}-\frac{12}{10}\right)\)

\(=\frac{13}{5}+\frac{7}{16}-\frac{11}{16}+\frac{12}{10}\)

\(=\left(\frac{13}{5}+\frac{12}{10}\right)+\left(\frac{7}{16}-\frac{11}{16}\right)\)

\(=\frac{19}{5}+\left(-\frac{1}{4}\right)\)

\(=\frac{71}{20}\)

a) \(-\left(\frac{3}{10}-\frac{6}{11}\right)-\left(\frac{21}{30}-\frac{5}{11}\right)\)

\(=\frac{-3}{10}+\frac{6}{11}-\frac{21}{30}+\frac{5}{11}\)

 \(=\left(\frac{-3}{10}-\frac{21}{30}\right)+\left(\frac{6}{11}+\frac{5}{11}\right)\)

\(=\left(\frac{-9}{30}-\frac{21}{30}\right)+1\)

\(=-1+1\)

= 0

b) \(\left(\frac{13}{5}+\frac{7}{16}\right)-\left(\frac{11}{16}-\frac{12}{10}\right)\)

\(=\frac{13}{5}+\frac{7}{16}-\frac{11}{16}+\frac{12}{10}\)

\(=\left(\frac{13}{5}+\frac{12}{10}\right)+\left(\frac{7}{16}-\frac{11}{16}\right)\)

\(=\left(\frac{26}{10}+\frac{12}{10}\right)-4\)

= \(\frac{19}{5}-4\)

= \(\frac{-1}{5}\)

a) \(-\left(\frac{3}{10}-\frac{6}{11}\right)-\left(\frac{21}{30}-\frac{5}{11}\right)\)

\(=\frac{-3}{10}+\frac{6}{11}-\frac{21}{30}+\frac{5}{11}\)

\(=\frac{-3}{10}+\frac{6}{11}-\frac{7}{10}+\frac{5}{11}\)

\(=\left(\frac{-3}{10}-\frac{7}{10}\right)+\left(\frac{6}{11}+\frac{5}{11}\right)\)

\(=-1+1\)

\(=0\)

b) \(\left(\frac{13}{5}+\frac{7}{16}\right)-\left(\frac{11}{16}-\frac{12}{10}\right)\)

\(=\frac{13}{5}+\frac{7}{16}-\frac{11}{16}+\frac{12}{10}\)

\(=\frac{13}{5}+\frac{7}{16}-\frac{11}{16}+\frac{6}{5}\)

\(=\left(\frac{13}{5}+\frac{6}{5}\right)+\left(\frac{7}{16}-\frac{11}{16}\right)\)

\(=\frac{19}{5}+\frac{-1}{4}\)

\(=\frac{76}{20}+\frac{-5}{20}\)

\(=\frac{71}{20}\)

Giá trị của biểu thức C tại x=25 là C(25).

Theo định lý Bezout, C(25) = số dư khi chia C(x) cho x-25.

Ta dùng sơ đồ Hooc-ne để tìm số dư này:

Vậy: C(25)=1 

\(\frac{21^{11}.5-7^{11}.3^{12}}{7^{10}.3^9+21^{10}}=\frac{7^{11}.3^{11}.5-7^{11}.3^{12}}{7^{10}.3^9+7^{10}.3^{10}}=\frac{7^{11}.3^{11}.\left(5-3\right)}{7^{10}.3^9.\left(1+3\right)}\)

                                            \(=\frac{7^{11}.3^{11}.2}{7^{10}.3^9.4}=\frac{7.3^2}{2}=\frac{7.9}{2}=\frac{63}{2}\)

nhân hết thì lm dc còn có cộng trừ thì hơi khó

Có cộng và trừ ko rút gon đc nhanh

a: =3/4-19/18-3/4

=-19/18

b: =24-24x47-24x54

=24(1-47-54)

=24x(-100)=-2400

a) \(=\dfrac{-19}{18}\)

b) \(=-2400\)

a:=-19/18

b: -2400

Tìm số tự nhiên x biết:

a) \(123+x=135\)

\(\Rightarrow x=135-123\)

\(\Rightarrow x=12\)

b) \(\left(x+15\right)-56=15\)

\(\Rightarrow x+15-56=15\)

\(\Rightarrow x=15-15+56\)

\(\Rightarrow x=0+56\)

\(\Rightarrow x=56\)

c) \(\left(x+3^3\right)\cdot6^3=3\cdot6^5\)

\(\Rightarrow x+3^3=\dfrac{3\cdot6^5}{6^3}\)

\(\Rightarrow x+3^3=3\cdot6^2\)

\(\Rightarrow x+27=108\)

\(\Rightarrow x=108-27\)

\(\Rightarrow x=81\)

a.    -2015 + ( -21 + 75 + 2015 ) = 0 + ( -21 ) + 75 = 54

b.    13 - 12 + 11 + 10 - 9 + 8 - 7 - 6 + 5 - 4 + 3 + 2 -1 = 1 + 11 + 1 + (-5) + 1 + 3 + 1 = 13

\(448\)

cho mình biết cả cách làm đi mấy bạn