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c: \(=\dfrac{-27\cdot100}{-30}=\dfrac{2700}{30}=90\)
1/ -3/4 > -7/8
2/ Thực hiện phép tính:
a) 3/4 - 7/6 + 9/8 = -5/12 + 9/8 = 17/24
b) -5/6 . 6/7 +1/7 = -5/7 + 1/7 = -4/7
c) -3/4 . 8/11 + -3/4 . 3/11 = -3/4 . (8/11 + 3/11) = -3/4 . 1 = -3/4
d) -3 1/4 - 1 1/4 + 0,25 = -13/4 - 5/4 + 1/4 = -9/2 + 1/4 = -17/4
- 27/1=81/3 (Ngược lại)
- 3/9=27/81 (Ngược lại)
- 27/9=3/1 (Ngược lại)
- 81/9=27/3 (Ngược lại)
- 1/27=3/81 (Ngược lại)
\(\dfrac{1}{1}\) = \(\dfrac{3}{3}\) = \(\dfrac{9}{9}\) = \(\dfrac{27}{27}\) = \(\dfrac{81}{81}\)
\(\left(2x-15\right)^5=\left(2x-15\right)^3\)
\(\Rightarrow\left(2x-15\right)^5-\left(2x-15\right)^3=0\)
\(\Rightarrow\left(2x-15\right)^3\left[\left(2x-15\right)^2-1\right]=0\)
\(\Rightarrow\left(2x-15\right)^3\left(2x-15-1\right)\left(2x-15+1\right)=0\)
\(\Rightarrow\left(2x-15\right)^3\left(2x-16\right)\left(2x-14\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}2x-15=0\\2x-16=0\\2x-14=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}2x=15\\2x=16\\2x=14\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{15}{2}\\x=8\\x=7\end{matrix}\right.\)
\(2xy+x+2y=13\\ \Rightarrow2xy+x+2y+1-1=13\\ \Rightarrow\left(2xy+2y\right)+\left(x+1\right)=13+1\\ \Rightarrow2y\left(x+1\right)+\left(x+1\right)=14\\ \Rightarrow\left(x+1\right)\left(2y+1\right)=14\\ \Rightarrow\left(x+1\right);\left(2y+1\right)\inƯ\left(14\right)\\ \Rightarrow\left(x+1\right);\left(2y+1\right)\in\left\{-14;-7;-2;-1;1;2;7;14\right\}\)
\(x+1\) | \(-14\) | \(-7\) | \(-2\) | \(-1\) | \(1\) | \(2\) | \(7\) | \(14\) |
\(2y+1\) | \(-1\) | \(-2\) | \(-7\) | \(-14\) | \(14\) | \(7\) | \(2\) | \(1\) |
\(x\) | \(-15\) | \(-8\) | \(-3\) | \(-2\) | \(0\) | \(1\) | \(6\) | \(13\) |
\(y\) | \(-1\) | \(-\dfrac{3}{2}\) | \(-4\) | \(-\dfrac{15}{2}\) | \(\dfrac{13}{2}\) | \(3\) | \(\dfrac{1}{2}\) | \(0\) |
Vì \(x,y\in N\Rightarrow\left(x;y\right)=\left(0;\dfrac{13}{2}\right),\left(1;3\right),\left(6;\dfrac{1}{2}\right),\left(13;0\right)\)
Vậy \(\left(x;y\right)=\left(0;\dfrac{13}{2}\right),\left(1;3\right),\left(6;\dfrac{1}{2}\right),\left(13;0\right)\)
\(1500-\left\{5^3\cdot2^3-11\left[7^2-5\cdot2^3+8\left(11^2-121\right)\right]\right\}\\ =1500-\left[125\cdot8-11\left(49-5\cdot8+8\cdot0\right)\right]\\ =1500-\left[125\cdot8-11\left(49-40+0\right)\right]\\ =1500-\left(125\cdot8-11\cdot9\right)\\ =1500-\left(1000-99\right)\\ =1500-901\\ =599\)
Lời giải:
4/7 quả bí nặng $1\frac{1}{2}$ kg = $\frac{3}{2}$ kg
Quả bi nặng: $\frac{3}{2}: \frac{4}{7}=2,625$ (kg)