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\(\Rightarrow12\times x+\left(4+6+...+26\right)=210\\ \Rightarrow12\times x+\dfrac{\left(26+4\right)\times12}{2}=210\\ \Rightarrow12\times x+180=210\\ \Rightarrow12\times x=30\\ \Rightarrow x=\dfrac{10}{4}\)
đoạn cuối là (x+26) à
nếu vậy thì giải như sau:
Dễ tính được là có 11 số hạng
=> 11x+154=210
<=> 11x=56
<=> x=56/11
lẻ vậy
b. \(\dfrac{4.2.3.5.2.6.2.5.3}{4.3.4.5.6.4.5.6}=\dfrac{1}{4}\)
c. \(\dfrac{17.2.101.2005}{17.2.101.2.2005}=\dfrac{1}{2}\)
d. \(\dfrac{2.3.4.2.11.13.17}{3.11.4.4.17.13.2}=\dfrac{1}{2}\)
a)\(\dfrac{4\times6\times10\times12\times15}{4\times12\times5\times24\times30}=\dfrac{2}{2\times2\times2}=\dfrac{2}{8}=\dfrac{1}{4}\)
b)\(\dfrac{34\times101\times2005}{17\times202\times4010}=\dfrac{2}{2\times2}=\dfrac{2}{4}=\dfrac{1}{2}\)
c)\(\dfrac{6\times8\times11\times13\times17}{33\times16\times17\times26}=\dfrac{6}{3\times2\times2}=\dfrac{1}{2}\)
= 13 x 2 x 8 + 4 x 13 - 10 x 2 x 13
= 13 x 16 + 4 x 13 - 20 x 13
= 13 x (16 + 4 - 20)
= 13 x 0
= 0
2/5 + 11/15 = 17/15
7/8 - 7/9 = 7/72
11/13 x 26/31 = 22/31
16/24 : 4 = 1/6
30 : 6/5 = 25
9/16 : 4 = 9/64
1/2 : 1/3 x 8/15 = 3/2 x 8/15 = 4/5
\(C,\dfrac{1}{2}.\dfrac{3}{4}+\dfrac{1}{2}.\dfrac{1}{4}=\dfrac{1}{2}.\left(\dfrac{3}{4}+\dfrac{1}{4}\right)\)
\(=\dfrac{1}{2}.\dfrac{4}{4}=\dfrac{1}{2}.1=\dfrac{1}{2}\)
\(D,\dfrac{11}{3}.\dfrac{26}{7}-\dfrac{26}{7}.\dfrac{8}{3}=\dfrac{26}{7}.\left(\dfrac{11}{3}-\dfrac{8}{3}\right)\)
\(=\dfrac{26}{7}.\dfrac{3}{3}=\dfrac{26}{7}.1=\dfrac{26}{7}\)
26*8+2*2*13-10*26
=26*8+2*26-10*26
=26*(8+2-10)
=26*0
=0
Nhớ tick mik nha
x = 2,5