|5x-2|< hoặc= 13
Giúp mình nhanh nhé! Mình cần gấp :3
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A=111+121+...+701
\(A = \left(\right. \frac{1}{11} + \frac{1}{12} + . . . + \frac{1}{20} \left.\right) + \left(\right. \frac{1}{21} + \frac{1}{22} + . . . + \frac{1}{30} \left.\right)\)
\(+ \left(\right. \frac{1}{31} + \frac{1}{32} + . . . + \frac{1}{40} \left.\right) + \left(\right. \frac{1}{41} + \frac{1}{42} + . . . + \frac{1}{50} \left.\right) + \left(\right. \frac{1}{51} + \frac{1}{52} + . . . + \frac{1}{60} \left.\right)\)
\(+ \left(\right. \frac{1}{61} + \frac{1}{62} + . . . + \frac{1}{70} \left.\right)\)
\(\Rightarrow A < \frac{1}{10} \cdot 10 + \frac{1}{20} \cdot 10 + \frac{1}{30} \cdot 10 + . . . + \frac{1}{60} \cdot 10\)
\(A < 1 + \frac{1}{2} + \frac{1}{3} + . . . + \frac{1}{6}\)
\(A < 1 + \frac{1}{2} + \frac{1}{3} + \frac{1}{6} + \left(\right. \frac{1}{4} + \frac{1}{5} \left.\right)\)
\(A < 2 + 0 , 45 < 2 , 5\)
A= 11 1 + 12 1 +...+ 70 1 A = ( 1 11 + 1 12 + . . . + 1 20 ) + ( 1 21 + 1 22 + . . . + 1 30 ) A=( 11 1 + 12 1 +...+ 20 1 )+( 21 1 + 22 1 +...+ 30 1 ) + ( 1 31 + 1 32 + . . . + 1 40 ) + ( 1 41 + 1 42 + . . . + 1 50 ) + ( 1 51 + 1 52 + . . . + 1 60 ) +( 31 1 + 32 1 +...+ 40 1 )+( 41 1 + 42 1 +...+ 50 1 )+( 51 1 + 52 1 +...+ 60 1 ) + ( 1 61 + 1 62 + . . . + 1 70 ) +( 61 1 + 62 1 +...+ 70 1 ) ⇒ A < 1 10 ⋅ 10 + 1 20 ⋅ 10 + 1 30 ⋅ 10 + . . . + 1 60 ⋅ 10 ⇒A< 10 1 ⋅10+ 20 1 ⋅10+ 30 1 ⋅10+...+ 60 1 ⋅10 A < 1 + 1 2 + 1 3 + . . . + 1 6 A<1+ 2 1 + 3 1 +...+ 6 1 A < 1 + 1 2 + 1 3 + 1 6 + ( 1 4 + 1 5 ) A<1+ 2 1 + 3 1 + 6 1 +( 4 1 + 5 1 ) A < 2 + 0 , 45 < 2 , 5 A<2+0,45<2,5
Đây qu, phiền bạn tick giup mình nha
x2+5.x=0
x.x+5.x=0
x.(x+5)=0
*x=0
*x+5=0
x=0-5
x=-5
Vậy x=0 hoặc x=-5
68 < x < 12
= > x \(\in\){ 60 ; 50 ; 40 ; 30 ; 20 ; 10 }
^^ Học tốt!
(-5)^2-(5x-3)=43
25 - ( 5x - -3 ) = 43
5x -3 = 25 - 43
5x -3 = - 18
5x = - 18 + 3
5x = -15
x = -15 : 5
x = -3
Hok tốt
\(\left(-5\right)^2-\left(5x-3\right)=43\)
\(\Rightarrow25-5x+3=43\)
\(\Rightarrow28-5x=43\)
\(\Rightarrow5x=28-43=-15\)
\(\Rightarrow x=-3\)
Vậy x = -3
\(\left|5x-2\right|\le13\)
\(\Rightarrow-13\le5x-2\le13\)
\(\Rightarrow-11\le5x\le13\)
\(\Rightarrow\frac{-11}{5}\le x\le\frac{13}{5}\)