3 x 5
5 x 7
7 x 9
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\(\dfrac{x-9}{55}+\dfrac{x-10}{66}=\dfrac{x-11}{77}+\dfrac{x-12}{88}\\ \Leftrightarrow\left(\dfrac{x-9}{55}+\dfrac{1}{11}\right)+\left(\dfrac{x-10}{66}+\dfrac{1}{11}\right)-\left(\dfrac{x-11}{77}+\dfrac{1}{11}\right)-\left(\dfrac{x-12}{88}+\dfrac{1}{11}\right)=0\)
\(\Leftrightarrow\left(\dfrac{x-9}{55}+\dfrac{5}{55}\right)+\left(\dfrac{x-10}{66}+\dfrac{6}{66}\right)-\left(\dfrac{x-11}{77}+\dfrac{7}{77}\right)-\left(\dfrac{x-12}{88}+\dfrac{8}{88}\right)=0\)
\(\Leftrightarrow\dfrac{x-4}{55}+\dfrac{x-4}{66}-\dfrac{x-4}{77}-\dfrac{x-4}{88}=0\)
\(\Leftrightarrow\left(x-4\right)\left(\dfrac{1}{55}+\dfrac{1}{66}-\dfrac{1}{77}-\dfrac{1}{88}\right)=0\\ \Leftrightarrow x=4\left(vì.\dfrac{1}{55}+\dfrac{1}{66}-\dfrac{1}{77}-\dfrac{1}{88}\ne0\right)\)
x^77+x^55+x^33+x^11+9=x^55(x^22+1)+x^11(x^22+)+x+9. phan h thanh hang dang thuc, ta thay hang dang thuc trong ngoac chia het cho x^2+1 nen du la x+9
78 - 55 = 23
96 : 3 = 32
43 + 77 = 120
17 X 9 = 153
(12 + 77 + 34 + 23 + 88 + 45 + 55 + 66) x (45200 – 1808 x 25)
=(12 + 77 + 34 + 23 + 88 + 45 + 55 + 66) x (45200-45200)
=(12 + 77 + 34 + 23 + 88 + 45 + 55 + 66) x 0
=0
a)\(\frac{20}{x}=\frac{x}{45}\)(Điều kiện x\(\ne0\))
<=>\(x^2=20.45\)
<=>\(x^2=900\)
<=>\(x=\pm30\)(Thỏa mãn)
Vậy.....
b)\(\frac{-25}{x}=\frac{-55}{77}\)(Điều kiện \(x\ne0\))
<=>(-55).x=(-25).77
<=>(-55).x=-1925
<=>x=(-1925):(-55)
<=>x=35
Vậy....
15
35
63
tk nha
3 x 5 = 15
5 x 7 = 35
7 x 9 = 63