Kết quả bằng 13 đúng không?

11 nha

bằng 13

chia ra làm các nhóm (13-12+11)+(10-9+8)-(7-6+5) -(4+3+2-1)

hay ta thấy 3 nhóm đầu có tổng  =số trừ trong các nhóm đó tức là 12+9-6+(4+3+2-1)

Hay= 23

ê câu này bằng13

1: ĐKXĐ:  \(x\notin\left\{0;3\right\}\)

\(\dfrac{x+3}{x}-\dfrac{x}{x-3}+\dfrac{9}{x^2-3x}\)

\(=\dfrac{x+3}{x}-\dfrac{x}{x-3}+\dfrac{9}{x\left(x-3\right)}\)

\(=\dfrac{\left(x+3\right)\left(x-3\right)-x^2+9}{x\left(x-3\right)}\)

\(=\dfrac{x^2-9-x^2+9}{x\left(x-3\right)}\)

=0

2: ĐKXĐ: \(x\notin\left\{0;1\right\}\)

\(\dfrac{3}{x}-\dfrac{5}{x-1}+\dfrac{3x+2}{x^2-x}\)

\(=\dfrac{3}{x}-\dfrac{5}{x-1}+\dfrac{3x+2}{x\left(x-1\right)}\)

\(=\dfrac{3x-3-5x+3x+2}{x\left(x-1\right)}\)

\(=\dfrac{x-1}{x\left(x-1\right)}=\dfrac{1}{x}\)

a)27*77+24*27-27=27*(77+24-1)=27*100=2700

b)(-12)+(-9)+121+|-20|=-21+121+20=100+20=120

c)2⁵*101-2⁵*101⁰=2⁵*101-2⁵*1=2⁵*(101-1)=32*100=3200

2700

120

3200

2700

120

3200

\(\frac{\left(-4\right)^6.9^5-\left(-6\right)^9.120.1^{2015}}{8^4.3^{12}-6^{11}.2016^0}=\frac{\left(2^2\right)^6.\left(3^2\right)^5+\left(2.3\right)^9.2^3.3.5.1}{\left(2^3\right)^4.3^{12}-\left(2.3\right)^{11}.1}=\frac{2^{12}.3^{10}+2^{12}.3^{10}.5}{2^{12}.3^{12}-2^{11}.3^{11}}\)

\(=\frac{2^{12}.3^{10}.\left(1+5\right)}{2^{11}.3^{11}.\left(2.3-1\right)}=\frac{2.6}{3.5}=\frac{4}{5}\)

\(\frac{\left(-4\right)^6.9^5-\left(-6\right)^9.120.1^{2015}}{8^4.3^{12}-6^{11}.2016^0}=\frac{\left(-2\right)^{12}.3^{10}+2^{12}.3^{10}.5}{2^{12}.3^{12}-2^{11}.3^{11}}=\frac{2^{12}.3^{10}.\left(1+5\right)}{2^{11}.3^{11}.\left(2.3-1\right)}=\frac{2.6}{3.5}=\frac{4}{5}\)

\(\text{Thực hiện phép tính}\)

   \(3\text{ × }\left(\frac{1}{7}+\frac{1}{3}-\frac{3}{14}\right) : \frac{11}{4}\)

\(=3\text{ x }\left(\frac{3}{21}+\frac{7}{21}-\frac{3}{14}\right)\text{ : }\frac{11}{4}\)

\(=3\text{ x }\left(\frac{10}{21}-\frac{3}{14}\right)\text{ : }\frac{11}{4}\)

\(=3\text{ x }\left(\frac{140}{294}-\frac{63}{294}\right)\text{ : }\frac{11}{4}\)

\(=3\text{ x }\frac{77}{294}\text{ : }\frac{11}{4}\)

\(=\frac{231}{294}:\frac{11}{4}\)

\(=\frac{231}{294}\text{ x }\frac{4}{11}\)

\(=\frac{924}{3234}=\text{Phân số này có thể rút gọn đó bạn ! Bạn tự rút gọn nha !}\)

   \(\left(\frac{21}{8}+\frac{1}{2}\right)\text{ : }\frac{5}{16}\)

\(=\left(\frac{21}{8}+\frac{4}{8}\right)\text{ : }\frac{5}{16}\)

\(=\frac{25}{8}\text{ : }\frac{5}{16}\)

\(=\frac{25}{8}\text{ x }\frac{16}{5}\)

\(=\frac{400}{40}=10\)

1/2*3+1/3*4+1/4*5 + 1/5*6 + .... + 1/99 * 100

= 1/2 -1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 +..... + 1/99 - 1/100

= 1/2 - 1/100 

= 49/100 nha bạn !

1/2x3+1/3x4+1/4x5+1/5x6+....+1/99x100

=1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+....+1/99-1/100

=1/2-1/100=49/100

1/2*3+1/3*4+1/4*5 + 1/5*6 + .... + 1/99 * 100

= 1/2 -1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 +..... + 1/99 - 1/100

= 1/2 - 1/100 

= 49/100

Đúng rồi nha bạn !