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0,5 . (-0,75) + 1,25 . (-0,5)
= 0,5 . ( - 0,75 - 0,5 )
= 0,5 . 2
= 1
tìm nghiệm của đa thức một biến:
a, x(x-5)-(x-5)*(3x+2)
b,2*(0,3x-0,5x)-0,5(3-x)
c,(x-1)-(x-2)=(-x-40-8
![](https://rs.olm.vn/images/avt/0.png?1311)
a. \(x\left(x-5\right)-\left(x-5\right)\left(3x+2\right)=0\)
\(\Rightarrow\left(x-5\right)\left[x-\left(3x+2\right)\right]=0\)
\(\Rightarrow\left(x-5\right)\left(x-3x-2\right)=0\)
\(\Rightarrow\left(x-5\right)\left(-2x-2\right)=0\)
\(\Rightarrow-2\left(x-5\right)\left(x+1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}-2\ne0\\x-5=0\\x+1=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}-2\ne0\\x=5\\x=-1\end{matrix}\right.\)
b. \(2\left(0,3x-0,5x\right)-0,5\left(3-x\right)=0\)
\(\Rightarrow-0,4x-1,5+0,5x=0\)
\(\Rightarrow0,1x-1,5=0\)
\(\Rightarrow0,1x=1,5\)
\(\Rightarrow x=\dfrac{1,5}{0,1}=15\)
c. \(\left(x-1\right)-\left(x-2\right)=\left(-x-40\right)-8\)
\(\Rightarrow x-1-x+2=-x-40-8\)
\(\Rightarrow1=-x-48\)
\(\Rightarrow1+48=-x\)
\(\Rightarrow x=-49\)
![](https://rs.olm.vn/images/avt/0.png?1311)
M = \(-0,5^2-4\left|-0,75\right|\)
\(=-0,25-4\cdot0,75\)
\(=-0,25-3=-3,25\)
~Học tốt~
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(-0,75\right)-\left(-1+\dfrac{2}{3}\right):0,5+\left(-\dfrac{1}{4}\right)\)
\(=\left(-0,75\right)-\left(-1-\dfrac{2}{3}\right)\cdot\dfrac{1}{2}-0,25\)
\(=\left(-0,75-0,25\right)+\dfrac{5}{6}\)
\(=-1+\dfrac{5}{6}\)
\(=-\dfrac{11}{6}\)
_________________
\(\left[\left(-\dfrac{3}{2}\right)+\dfrac{2}{3}\right]^2\cdot\dfrac{24}{25}-\dfrac{1}{5}\)
\(=\left(-\dfrac{9}{6}+\dfrac{4}{6}\right)^2\cdot\dfrac{24}{25}-\dfrac{1}{5}\)
\(=\left(\dfrac{-5}{6}\right)^2\cdot\dfrac{24}{25}-\dfrac{1}{5}\)
\(=\dfrac{25}{36}\cdot\dfrac{24}{25}-\dfrac{1}{5}\)
\(=\dfrac{2}{3}-\dfrac{1}{5}\)
\(=\dfrac{7}{15}\)
\(a,\left(-0,75\right)-\left(-1+\dfrac{2}{3}\right):0,5-\dfrac{1}{4}\\ =-\dfrac{3}{4}-\left(\dfrac{-3+2}{3}\right):\dfrac{1}{2}-\dfrac{1}{4}\\ =-\dfrac{3}{4}-\left(-\dfrac{1}{3}\right):\dfrac{1}{2}-\dfrac{1}{4}\\ =-\dfrac{3}{4}-\left(-\dfrac{1}{3}\right)\times2-\dfrac{1}{4}\\ =-\dfrac{3}{4}+\dfrac{2}{3}-\dfrac{1}{4}\\ =\left(-\dfrac{3}{4}-\dfrac{1}{4}\right)+\dfrac{2}{3}\\ =-\dfrac{4}{4}+\dfrac{2}{3}\\ =-1+\dfrac{2}{3}\\ =\dfrac{-3+2}{3}=-\dfrac{1}{3}\)
\(b,\left[\left(-\dfrac{3}{2}\right)+\dfrac{2}{3}\right]^2\times\dfrac{24}{25}-\dfrac{1}{5}\\ =\left(\dfrac{-3\times3+2\times2}{6}\right)^2\times\dfrac{24}{25}-\dfrac{1}{5}\\ =\left(-\dfrac{5}{6}\right)^2\times\dfrac{24}{25}-\dfrac{1}{5}\\ =\dfrac{25}{36}\times\dfrac{24}{25}-\dfrac{1}{5}\\ =\dfrac{2}{3}-\dfrac{1}{5}\\ =\dfrac{2\times5-3}{15}=\dfrac{7}{15}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a: Xét ΔABH vuông tại H và ΔACH vuông tại H có
AB=AC
AH chung
=>ΔABH=ΔACH
b: HI//AB
=>góc IHA=góc BAH
=>góc IHA=góc IAH
=>ΔIAH cân tại I
c: Xét ΔBAC có
H là trung điểm của CB
HI//AB
=>I là trung điểm của AC
![](https://rs.olm.vn/images/avt/0.png?1311)
`@` `\text {Ans}`
`\downarrow`
`a,`
`3,27 - 4,15`
`= -0,88`
`b,`
`-5,5 + (-2,85)`
`= -5,5 - 2,85`
`= -8,35`
`c,`
`0,67 + 1,56`
`= 2,23`
`d,`
`7,86 + (-5,3)`
`= 7,86 - 5,3`
`= 2,56`
`e,`
`4,5 - (-9,5)`
`= 4,5 + 9,5`
`= 14`
`f,`
`0,5*1,5`
`= 0,75`
`i,`
`0,6 \div 1,5`
`= 0,4`
`k,`
`0,75 \div (-0,4)`
`= -1,875`
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có : A=\(\dfrac{0,5+\dfrac{7}{12}-\dfrac{5}{6}}{1-\dfrac{2}{3}+0,75}=\dfrac{\dfrac{1}{2}+\dfrac{7}{12}-\dfrac{5}{6}}{1-\dfrac{2}{3}+\dfrac{3}{4}}=\dfrac{\dfrac{1}{4}}{\dfrac{13}{12}}=\dfrac{13}{48}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{0.375-0.3+\dfrac{3}{11}+\dfrac{3}{12}}{-0.625+0.5-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{1.5+1-0.75}{2.5+\dfrac{5}{3}-1.25}\)
=\(\dfrac{\dfrac{3}{8}-\dfrac{3}{10}+\dfrac{3}{11}+\dfrac{3}{12}}{-\dfrac{5}{8}+\dfrac{5}{10}-\dfrac{5}{11}-\dfrac{5}{12}}+\dfrac{\dfrac{3}{2}+\dfrac{3}{3}-\dfrac{3}{4}}{\dfrac{5}{2}+\dfrac{5}{3}-\dfrac{5}{4}}\)
=\(\dfrac{3.\left(\dfrac{1}{8}-\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}\right)}{-5.\left(\dfrac{1}{8}-\dfrac{1}{10}+\dfrac{1}{11}+\dfrac{1}{12}\right)}+\dfrac{3\cdot\left(\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\right)}{5\cdot\left(\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}\right)}\)
=\(\dfrac{3}{-5}+\dfrac{3}{5}\)
=\(0\)
0,5x(-0,75)+1,25x(-0,5)
= -0,375 + (-0,625)
= -1
\(0,5 \times(-0,75)+1,25 \times (-0,5)\)
\(=(-0,5) \times (0,75+1,25)\)
\(=(-0,5) \times 2=-1\)