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a) 37,5 . 6,5 – 7,5 . 3,4 – 6,6 . 7,5 + 3,5 . 37,5
= (37,5 . 6,5 + 3,5 . 37,5) - (7,5 . 3,4 + 6,6 . 7,5)
= 37,5(6,5 + 3,5) - 7,5(3,4 + 6,6)
= 37,5 . 10 - 7,5 . 10
= 375 - 75 = 300.
b) 452 + 402 – 152 + 80 . 45 = 452 +2 . 40 . 45 + 402 – 152
= (40 + 45)2 – 152 = 852 – 152 = (85 – 15)(85 + 15) = 70 . 100 = 7000.
c ) \(\left|3,4-2x\right|:\frac{1}{2}=\frac{3}{4}\)
\(\left|3,4-2x\right|=\frac{3}{8}\)
\(\Rightarrow\left[\begin{array}{nghiempt}3,4-2x=\frac{3}{8}\\3,4-2x=-\frac{3}{8}\end{array}\right.\Rightarrow\left[\begin{array}{nghiempt}x=\frac{121}{80}\\x=\frac{151}{80}\end{array}\right.\)
Vậy ...........
e) \(\left|x+2,8\right|=3,5\)
\(\Rightarrow\left[\begin{array}{nghiempt}x+2,8=3,5\\x+2,8=-3,5\end{array}\right.\Rightarrow\left[\begin{array}{nghiempt}x=0,7\\x=-6,3\end{array}\right.\)
Vậy ....................
f ) \(2.\left|2x-3\right|=\frac{1}{2}\)
\(\left|2x-3\right|=\frac{1}{4}\)
\(\Rightarrow\left[\begin{array}{nghiempt}2x-3=\frac{1}{4}\\2x-3=-\frac{1}{4}\end{array}\right.\Rightarrow\left[\begin{array}{nghiempt}x=\frac{13}{8}\\x=\frac{11}{8}\end{array}\right.\)
Vậy ................
g ) \(7,5-3.\left|5-2x\right|=4,5\)
\(3.\left|5-2x\right|=4,5\)
\(\left|5-2x\right|=\frac{3}{2}\)
\(\Rightarrow\left[\begin{array}{nghiempt}5-2x=\frac{3}{2}\\5-2x=-\frac{3}{2}\end{array}\right.\Rightarrow\left[\begin{array}{nghiempt}x=\frac{7}{4}\\x=\frac{13}{4}\end{array}\right.\)
Vậy ..............
\(\frac{x+15}{x}=\frac{4}{3}\)
\(\Rightarrow3\left(x+15\right)=4x\)
\(3x+45=4x\)
\(4x-3x=45\)
\(x=45\)
\(\frac{7,5-x}{3,5+x}=\frac{x+40}{x+70}\)
\(\Rightarrow\left(7,5-x\right)\left(x+70\right)=\left(3,5+x\right)\left(x+40\right)\)
\(7,5x+525-x^2-70x=3,5x+140+x^2+40x\)
\(4x+385-2x^2=110x\)
\(385-2x^2=106x\)
Đề sai òi bạn ~ nếu cái đề này thì x = 412372022 ...... số vô tỉ =.= bậc lên cũng cũng không được số hữa tỉ nào auto ...
452 + 402 - 152 + 80.45 = (402 + 2.40.45 + 452) - 152
= (40+45)2 - 152
= (40+45-15).(40+45+15)
= 70.100 = 7000
\(A=\left(2\frac{1}{3}+3,5\right):\left(-4\frac{1}{6}+3\frac{1}{7}\right)+7,5\)
\(A=\left(\frac{7}{3}+3,5\right):\left(\frac{-25}{6}+\frac{22}{7}\right)+7,5\)
\(A=\frac{35}{6}:\frac{-43}{42}+7,5\)
\(A=\frac{-245}{43}+7,5\)
\(A=\frac{155}{86}\)
\(M=\left(2\dfrac{1}{3}+3,5\right):\left(-4\dfrac{1}{6}+3\dfrac{1}{7}\right)+7,5\)
\(M=\left(\dfrac{7}{3}+\dfrac{7}{2}\right):\left(-\dfrac{25}{6}+\dfrac{22}{7}\right)+\dfrac{15}{2}\)
\(M=\dfrac{35}{6}:\left(-\dfrac{43}{42}\right)+\dfrac{15}{2}\)
\(M=\left(-\dfrac{245}{43}\right)+\dfrac{15}{2}\)
\(M=\dfrac{155}{86}\)
M=(213+3,5):(−416+317)+7,5M=(213+3,5):(−416+317)+7,5
M=(73+72):(−256+227)+152M=(73+72):(−256+227)+152
M=356:(−4342)+152M=356:(−4342)+152
M=(−24543)+152M=(−24543)+152
M=15586M=15586
\(M=\left(2\frac{1}{3}+3,5\right):\left(-4\frac{1}{6}+3\frac{1}{7}\right)+7,5\)
\(=\left(\frac{7}{3}+\frac{7}{2}\right):\left(\frac{-25}{6}+\frac{22}{7}\right)+\frac{15}{2}\)
\(=\left(\frac{14}{6}+\frac{21}{6}\right):\left(\frac{-175}{42}+\frac{132}{42}\right)+\frac{15}{2}\)
\(=\frac{14+21}{6}:\frac{-175+132}{42}+\frac{15}{2}\)
\(=\frac{35}{6}:\frac{-43}{42}+\frac{15}{2}=\frac{35}{6}.\frac{-42}{43}+\frac{15}{2}\)
\(=\frac{-245}{43}+\frac{15}{2}=\frac{-490}{86}+\frac{645}{86}\)
\(=\frac{-490+645}{86}=\frac{155}{86}\)
\(a,\frac{x+15}{x}=\frac{4}{3}\Rightarrow4x=3x+45\Leftrightarrow x=45\)
\(b,\frac{7,5-x}{3,5+x}=\frac{5}{6}\Rightarrow17,5+5x=45-6x\Leftrightarrow11x=27,5\Rightarrow x=2,5\)
\(c,\frac{x-20}{x-10}=\frac{x+40}{x+70}\Rightarrow\left(x-20\right)\left(x+70\right)=\left(x-10\right)\left(x+40\right)\)
\(\Leftrightarrow x^2+50x-1400=x^2+30x-400\)
\(\Leftrightarrow20x=1000\)
\(\Rightarrow x=50\)
a)\(37.x6.5-7.5x3.4-6.6x7.5+3.5x37.5\)
=\(7.5x5x6.5-7.5x3.4-6.6x7.5+3.5x7.5x5\)
=\(7.5x\left(5x6.5-3.4-6.6+3.5x5\right)\)
=\(7.5x\left(2x6.5-10\right)\)
=\(7.5x\left(13-10\right)\)
=\(7.5x3\)
=\(22.5\)
Phần b phải là \(45^3\)chứ bạn