Phần típ theo nè!
Câu 5: Tìm \(x\):
Đề bài : \(xxx\) - \(x
\) x 105 = 30
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Câu 6: Tìm \(x \):
a) \(x \) x 7 + \(x\) = 384.
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b) \( x\)\(x
\) - \(x\) x 2 = 378.
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Câu 7: Tìm số tự nhiên ab biết ab x 9 = 2ab :
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Câu 8: Viết biểu thức sau thành tích 2 thừa số:
Đề bài: ab + ab x 2 + ab x 4 + ab =
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-------- Còn nữa -------
\(\left(x+2\right)+\left(x+5\right)+\left(x+8\right)+...+\left(x+77\right)=1417\)
\(x+2+x+5+x+8+...+x+77=1417\)
\(x\left(\frac{77-2}{3}+1\right)+\left(77+2\right)\text{x}\frac{\left(77-2\right):3+1}{2}=1417\)
\(26x+79\text{x}\frac{25+1}{2}=1417\)
\(26x+79\text{x}13=1417\)
\(26x+1027=1417\)
\(26x=1417-1027\)
\(26x=390\)
\(x=390:26\)
\(x=15\)