tìm x biết
- \(x\times\left(4.6+\frac{3}{5}\right)+7.2-8.15\)
- \(42+\frac{3}{7}\times\left[3\times-1\right]=12\)
- \(\left[2\times x-1\right]=\left[x+2\right]\)
- \(\frac{x+2}{5}=\frac{2-3\times x}{3}\)
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\(a,\)\(-\frac{3}{5}\cdot x=\frac{1}{4}+0,75\)
\(-\frac{3}{5}\cdot x=\frac{1}{4}+\frac{3}{4}=\frac{4}{4}=1\)
\(x=1\div\left(-\frac{3}{5}\right)\)
\(x=-\frac{5}{3}\)
\(b,\)\(\left(\frac{1}{7}-\frac{1}{3}\right)\cdot x=\frac{28}{5}\times\left(\frac{1}{4}-\frac{1}{7}\right)\)
\(\left(\frac{3}{21}-\frac{7}{21}\right)\cdot x=\frac{28}{5}\cdot\left(\frac{7}{28}-\frac{4}{28}\right)\)
\(-\frac{4}{21}\cdot x=\frac{28}{5}\cdot\frac{3}{28}\)
\(-\frac{4}{21}\cdot x=\frac{3}{5}\)
\(x=\frac{3}{5}\div\left(-\frac{4}{21}\right)\)
\(x=-\frac{63}{20}\)
\(c,\)\(\frac{5}{7}\cdot x=\frac{9}{8}-0,125\)
\(\frac{5}{7}\cdot x=\frac{9}{8}-\frac{1}{8}\)
\(\frac{5}{7}\cdot x=1\)
\(x=1\div\frac{5}{7}\)
\(x=\frac{7}{5}\)
\(d,\)\(\left(\frac{2}{11}+\frac{1}{3}\right)\cdot x=\left(\frac{1}{7}-\frac{1}{8}\right)\cdot36\)
\(\left(\frac{6}{33}+\frac{11}{33}\right)\cdot x=\left(\frac{8}{56}-\frac{7}{56}\right)\cdot36\)
\(\frac{17}{33}\cdot x=\frac{1}{56}\cdot36\)
\(\frac{17}{33}\cdot x=\frac{9}{14}\)
\(x=\frac{9}{14}\div\frac{17}{33}\)
\(x=\frac{9}{14}\cdot\frac{33}{17}=\frac{297}{238}\)
\(\Leftrightarrow\frac{4x^2}{5}\times\frac{2x-3}{6}-\frac{3x-10}{15}\times\frac{4x^2+3}{3}=\frac{22x^2}{45}\)
\(\Leftrightarrow\frac{4x^2\left(2x-3\right)}{30}-\frac{\left(3x-10\right)\left(4x^2+3\right)}{45}=\frac{22x^2}{45}\)
\(\Leftrightarrow\frac{12x^2\left(2x-3\right)}{90}-\frac{2\left(3x-10\right)\left(4x^2+3\right)}{90}=\frac{44x^2}{90}\)
\(\Leftrightarrow12x^2\left(2x-3\right)-2\left(3x-10\right)\left(4x^2+3\right)=44x^2\)
\(\Leftrightarrow24x^2-36x^2-2\left(12x^3+9x-40x^2-30\right)=44x^2\)
\(\Leftrightarrow24x^2-36x^2-24x^3-18x+80x^2+60=44x^2\)
\(\Leftrightarrow24x^3-36x^2-24x^3-18x+80x^2-44x^2=-60\)
\(\Leftrightarrow\left(24x^3-24x^3\right)+\left(-36x^2+80x^2-44x^2\right)-18x=-60\)
\(\Leftrightarrow-18x=-60\)
\(\Leftrightarrow x=\frac{-60}{-18}\)
\(\Leftrightarrow x=\frac{10}{3}\)
Bài 1:
a) \(\frac{2}{5}+\frac{1}{5}.\left(\frac{3}{4}\right)\)
= \(\frac{2}{5}+\frac{3}{20}\)
= \(\frac{11}{20}\)
b) \(\frac{5}{12}.\left(-\frac{3}{4}\right)\) + \(\frac{7}{12}.\left(-\frac{3}{4}\right)\)
= \(\left(\frac{5}{12}+\frac{7}{12}\right).\left(-\frac{3}{4}\right)\)
= 1.\(\left(-\frac{3}{4}\right)\)
= \(-\frac{3}{4}\)
Còn câu c) đang nghĩ.
Bài 2:
a) \(\frac{5}{7}+\frac{2}{7}\)x = 1
1.x = 1
x = 1 : 1
x = 1
Vậy x = 1.
b) 0,2 + | x - 1, 3 = 1, 5|
0,2 + x = 1, 5 + 1, 3
0,2 + x = 2, 8
x = 2, 8 - 0, 2
x = 2, 6
Vậy x = 2, 6.
c) 2x + 5 = 37
2x = 37 - 5
2x = 32
2x = 25
=> x = 5
Vậy x = 5.
d) 2x + 2x + 1 = 48
2x . 1 + 2x . 21 = 48
2x . ( 1 + 2) = 48
2x . 3 = 48
2x = 48 : 3
2x = 16
2x = 24
=> x = 4
Vậy x = 4.
Chúc bạn học tốt!
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thanks
a) Thiếu đề (hoặc sai)
b) x đâu?
c)\(3x-1=x+2\)
\(\Rightarrow3x-x=2+1\)
\(\Rightarrow2x=3\)
\(\Rightarrow x=\frac{3}{2}\)
c) \(\frac{x+2}{5}=\frac{2-3x}{3}\)
\(\Rightarrow3.\left(x+2\right)=5.\left(2-3x\right)\)
\(\Rightarrow3x+6=10-15x\)
\(\Rightarrow3x+15x=10-6\)
\(\Rightarrow18x=4\)
\(\Rightarrow x=\frac{4}{18}=\frac{2}{9}\)
câu 1 là \(x\times\left(4.6+\frac{3}{5}\right)=7.2-8.15\)
câu 2 là \(42+\frac{3}{7}.\left[3\times x-1=12\right]\)