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1,
\(\dfrac{6}{7}\) + \(\dfrac{-5}{8}\) : (-5) -\(\dfrac{3}{16}\) . \(\left(-2\right)^2\)
= \(\dfrac{6}{7}\) + \(\dfrac{-5}{8}\) . \(\dfrac{-1}{5}\) - \(\dfrac{3}{16}\) . 4
= \(\dfrac{6}{7}\) + \(\dfrac{1}{8}\) - \(\dfrac{3}{4}\)
= \(\dfrac{48}{56}\) + \(\dfrac{7}{56}\) - \(\dfrac{42}{56}\)
= \(\dfrac{13}{56}\)
3,
a,\(\dfrac{3}{5}\)x - \(\dfrac{7}{10}\)x = \(\dfrac{-1}{2}\)
x.(\(\dfrac{3}{5}\) - \(\dfrac{7}{10}\)) = \(\dfrac{-1}{2}\)
x.\(\dfrac{-1}{10}\)= \(\dfrac{-1}{2}\)
x =\(\dfrac{-1}{2}\):\(\dfrac{-1}{10}\)
x = 5
c, (2,5x - 3,6) : \(\dfrac{15}{7}\) = -1
( \(\dfrac{5}{2}\)x - \(\dfrac{18}{5}\)) : \(\dfrac{15}{7}\) = -1
\(\dfrac{5}{2}\)x - \(\dfrac{18}{5}\) = -1 . \(\dfrac{15}{7}\)
\(\dfrac{5}{2}\)x - \(\dfrac{18}{5}\) = \(\dfrac{-15}{7}\)
\(\dfrac{5}{2}\)x = \(\dfrac{-15}{7}\) + \(\dfrac{18}{5}\)
\(\dfrac{5}{2}\)x = \(\dfrac{51}{35}\)
x =\(\dfrac{51}{35}\) : \(\dfrac{5}{2}\)
x = \(\dfrac{102}{175}\)
Mình không biết có chỗ nào sai không nữa.
\(a,-\dfrac{13}{20}+x=\dfrac{-11}{15}\\ \Rightarrow x=\dfrac{-11}{15}+\dfrac{13}{20}\\ \Rightarrow x=-\dfrac{1}{12}\\ b,\left(x-3,5\right):3\dfrac{1}{2}-2,5=-1\dfrac{3}{4}\\ \Rightarrow\left(x-\dfrac{7}{2}\right):\dfrac{7}{2}-\dfrac{5}{2}=\dfrac{-7}{4}\\ \Rightarrow\left(x-\dfrac{7}{2}\right):\dfrac{7}{2}=\dfrac{3}{4}\\ \Rightarrow x-\dfrac{7}{2}=\dfrac{21}{8}\\ \Rightarrow x=\dfrac{49}{8}\)
5:
a: \(3^{2n}=\left(3^2\right)^n=9^n\)
\(\left(2^{3n}\right)=\left(2^3\right)^n=8^n\)
=>\(3^{2n}>2^{3n}\)
b: \(199^{20}=\left(199^4\right)^5=1568239201^5\)
\(2003^{15}=\left(2003^3\right)^5=8036054027^5\)
mà \(1568239201< 8036054027\)
nên \(199^{20}< 2003^{15}\)
4: \(100< 5^{2x-1}< 5^6\)
mà \(25< 100< 125\)
nên \(125< 5^{2x-1}< 5^6\)
=>3<2x-1<6
=>4<2x<7
=>2<x<7/2
mà x nguyên
nên x=3
a: \(\Leftrightarrow\left(x-\dfrac{2}{5}\right):\dfrac{3}{2}=-\dfrac{5}{4}+\dfrac{5}{2}=\dfrac{5}{4}\)
\(\Leftrightarrow x-\dfrac{2}{5}=\dfrac{5}{4}\cdot\dfrac{3}{2}=\dfrac{15}{8}\)
hay x=91/40
b: \(\Leftrightarrow\left(2.5x-3.6\right)=-1\cdot\dfrac{12}{7}=\dfrac{-12}{7}\)
=>2,5x=66/35
hay x=132/175
c: \(\Leftrightarrow\left(\dfrac{15}{4}-2x\right)=\dfrac{19}{9}:\dfrac{4}{3}=\dfrac{19}{9}\cdot\dfrac{3}{4}=\dfrac{19}{12}\)
=>2x=15/4-19/12=45/12-19/12=26/12
=>x=13/12
a) Ta có: X-1,25x4= 2,5
=)X-1,25= 2,5:4= 0,625
=)X= 0,625+1,25= 1,875
Vậy X= 1,875
b) Ta có: (X+1)+(X+2)+(X+3)+...+(X+20) = 750
=)X+1+X+2+X+3+...+X+20(20 chữ số X) = 750
=)20X+(1+2+3+...+20) = 750
=)20X+[(1+20)+(2+19)+...+(10+11)] = 750 (10 cặp số hạng)
=)20X+(21+21+21+...+21) = 750
=)20X+21x10 = 750
=)20X+210 = 750
=)20X = 750-210 = 540
=)X = 540:20 = 27
Vậy X = 27
Câu C bạn nhìn phần B rồi tự nghĩ nha. Luời quá rồi
bn ơi ko thì bn làm từng phép một cũng đc nhé các bn giải hộ mình mai mình phải nộp rồi
1) a) 4⁸.2²⁰ = (2²)⁸.2²⁰
= 2¹⁶.2²⁰ = 2³⁶
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9¹².27⁵.81³ = (3²)¹².(3³)⁵.(3⁴)⁴
= 3²⁴.3¹⁵.3¹⁶ = 3⁵⁵
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64³.4⁵.16² = (4³)³.4⁵.(4²)²
= 4⁹.4⁵.4⁴ = 4¹⁸
b) 25²⁰.125⁴ = (5²)²⁰.(5³)⁴
= 5⁴⁰.5¹² = 5⁵²
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x⁷.x³.x⁴ = x¹⁴
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3⁶.4⁶ = (3.4)⁶ = 12⁶
2) a) 2² = 4
2³ = 8
2⁴ = 16
2⁵ = 32
2⁶ = 64
2⁷ = 128
2⁸ = 256
2⁹ = 512
2¹⁰ = 1024
b) 3² = 9
3³ = 27
3⁴ = 81
3⁵ = 243
c) 4² = 16
4³ = 64
4⁴ = 256
d) 5² = 25
5³ = 125
5⁴ = 625