tính hợp lý
87 x (- 17) + (- 83) x 87
(- 45) x (1 + 432) - 432 x (- 45)
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432/45 + 14.7 = 24.3
823.2 / 8.4 - 98 = 0
(754.4 + 333.1 ) / 12.5 = 87
\(\frac{432}{45}+x=24,3\)
\(\Leftrightarrow9,6+x=24,3\)
\(\Leftrightarrow x=24,3-9,6=14,7\)
\(823,2:84-x=0\)
\(\Leftrightarrow98-x=0\Leftrightarrow x=98\)
\(\frac{754,4+333,1}{x}=87\)
\(\Leftrightarrow754,4+333,1=87x\)
\(\Leftrightarrow1087,5=87x\)
\(\Rightarrow x=1087,5:87=12,5\)
a)
\(\frac{864\cdot48-432\cdot96}{864\cdot48\cdot432}=\frac{432\cdot2\cdot48-432\cdot96}{864\cdot48\cdot432}=\frac{432\cdot96-432\cdot96}{864\cdot48\cdot432}=\frac{0}{864\cdot48\cdot432}=0\)
Làm từng phần một nha =))
b)
\(\frac{16\cdot17-5}{16\cdot16+11}=\frac{16\cdot\left(16+1\right)-5}{16\cdot16+11}=\frac{16^2+16-5}{16^2+11}=\frac{16^2+11}{16^2+11}=1\)
@_@
\(70-5\cdot\left(x-3\right)=45\)
\(\Rightarrow5\cdot\left(x-3\right)=70-45\)
\(\Rightarrow5\cdot\left(x-3\right)=25\)
\(\Rightarrow x-3=\dfrac{25}{5}\)
\(\Rightarrow x-3=5\)
\(\Rightarrow x=5+3=8\)
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\(10+2\cdot x=4^5:4^3\)
\(\Rightarrow10+2\cdot x=4^2\)
\(\Rightarrow10+2\cdot x=16\)
\(\Rightarrow2\cdot x=16-10\)
\(\Rightarrow2\cdot x=6\)
\(\Rightarrow x=\dfrac{6}{2}=3\)
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\(2\cdot x-138=2^3\cdot3^2\)
\(\Rightarrow2\cdot x-138=72\)
\(\Rightarrow2\cdot x=72+138\)
\(\Rightarrow2\cdot x=210\)
\(\Rightarrow x=\dfrac{210}{2}=105\)
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\(231-\left(x-6\right)=1339:12\)
\(\Rightarrow231-x+6=1339:12\)
\(\Rightarrow237-x=\dfrac{1339}{12}\)
\(\Rightarrow x=237-\dfrac{1339}{12}\)
\(\Rightarrow x=\dfrac{1505}{12}\)
=87.(-17+(-83)=87.(-100)=-8700
=-45.(1+432-432)=-45.1=-45
a, =87[-17+(-83)]
=87.(-100)
=-8700
b, =(-45)+-(45).432-432.(-45)
(-45)+(-45)(432-432)
=(-45)+0
=-45