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Đáp án:
$\\$
`14,`
`[ (8x - 12) ÷ 4] × 3^6 = 3^9`
`⇔ (8x- 12) ÷ 4 = 3^9 ÷ 3^6`
`⇔ (8x -12) ÷4=3^3`
`⇔ (8x - 12) ÷4 = 27`
`⇔ 8x - 12 = 27×4`
`⇔8x-12 = 108`
`⇔8x=108 + 12`
`⇔8x=120`
`⇔x=120÷8`
`⇔x=15`
Vậy `x=15`
$\\$
`15,`
`220 + [2^4 + (x-5)] = 8^2 × 5`
`⇔ 220 + [16 + (x-5)] = 64 × 5`
`⇔ 220 + [16 + (x-5)]=320`
`⇔ 16 + (x-5) = 320 - 220`
`⇔ 16 + (x-5) =100 `
`⇔ x-5 =100- 16`
`⇔ x-5= 84`
`⇔x=84 + 5`
`⇔x=89`
Vậy `x=89`
$\\$
`16,`
`213 - (x - 6) = 1236 ÷ 12`
`⇔ 213 - (x-6)=103`
`⇔ x-6 = 213 - 103`
`⇔x-6=110`
`⇔x=110 + 6`
`⇔x=116`
Vậy `x=116`
$\\$
`17,`
`3 (2x - 1)^3 - 1^{2020} = 5 × 4^2`
`⇔ 3 (2x - 1)^3 - 1 = 5 × 16`
`⇔ 3 (2x - 1)^3 - 1 =80`
`⇔ 3 (2x-1)^3 = 80 + 1`
`⇔ 3 (2x-1)^3 = 81`
`⇔ (2x-1)^3 = 81 ÷ 3`
`⇔ (2x-1)^3=27`
`⇔ (2x-1)^3 = 3^3`
`⇔ 2x-1=3`
`⇔2x=3+1`
`⇔2x=4`
`⇔x=4÷2`
`⇔x=2`
Vậy `x=2`
$\\$
`18,`
`18+ |x + 7| = 9 - (-11)`
`⇔ 18 + |x + 7| = 20`
`⇔ |x + 7| = 20 - 18`
`⇔ |x + 7| = 2`
`⇔` \(\left[ \begin{array}{l}x+7=2\\x+7=-2\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=-5\\x=-9\end{array} \right.\)
Vậy `x=-5` hoặc `x=-9`
$\\$
`19,`
`-x + 5 = 3x - 11`
`⇔ -x - 3x=-5 - 11`
`⇔ -4x = -16`
`⇔ x = -16 ÷ (-4)`
`⇔ x=4`
Vậy `x=4`
$\\$
`20,`
`2x + 5 + (x-7) = -3 + 22`
`⇔ 2x + 5 + x- 7 = 19`
`⇔ (2x + x) + (5-7) = 19`
`⇔ 3x - 2 = 19`
`⇔ 3x = 19 + 2`
`⇔ 3x = 21`
`⇔x=21÷3`
`⇔x=7`
Vậy `x=7`
$\\$
`21,`
`(x + 4) (1 + |x - 2|) = 0`
`⇔` \(\left[ \begin{array}{l}x+4=0\\1 + |x - 2| = 0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=0-4\\|x-2| = -1 \text{(Vô lí)}\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=-4\\x=∅\end{array} \right.\)
Vậy `x=-4`
$\\$
`22,`
`2 (x-3) - 3^2 = 3 (x + 1) + 2`
`⇔ 2x - 6 - 9 = 3x + 3 + 2`
`⇔ 2x - 15 = 3x + 5`
`⇔ 2x - 3x = 15 + 5`
`⇔ -x = 20`
`⇔ x=-20`
Vậy `x=-20`
$\\$
`23,`
`(x-1) + (x-2) + ... + (x-20) = 150`
`⇔ x- 1 + x - 2 + ... + x-20 = 150`
`⇔ (x + x + ... + x) - (1 + 2 + .. + 20) = 150`
`⇔ 20x - ( (20 + 1) × 20)/2 = 150`
`⇔ 20x - 210 = 150`
`⇔ 20x = 150 + 210`
`⇔ 20x = 360`
`⇔ x = 360 ÷ 20`
`⇔ x = 18`
Vậy `x=18`
$\\$
`24,`
`(98 - x) + (96 - x) + ... + (2- x) = 2205`
`⇔ 98 - x + 96 - x + ... + 2 - x = 2205`
`⇔ (98 + 96 + .. + 2) - (x + x + .. + x) = 2205`
`⇔ ( (98 + 2) × 49)/2 - 49x = 2205`
`⇔ 2450 - 49x = 2205`
`⇔ 49x = 2450 - 2205`
`⇔ 49x = 245`
`⇔ x = 245 ÷ 49`
`⇔ x = 5`
Vậy `x=5`
Hãy giúp mọi người biết câu trả lời này thế nào?
4027
3515
Đáp án:
`14)[(8x-12):4].3^6=3^9`
`=>[4(2x-3):4]=3^9:3^6`
`=>2x-3=3^3=27`
`=>2x=30`
`=>x=15`
Vậy `x=15`.
`15)220+[2^4+(x-5)]=8^2*5`
`=>220+(16+x-5)=64*5`
`=>220+x+11=320`
`=>x+11=320-220=100`
`=>x=100-11=89`
Vậy `x=89`.
`16)213-(x-6)=1236:12`
`=>213-(x-6)=103`
`=>213-103=x-6`
`=>110=x-6`
`=>x=116`
Vậy `x=116`
`17)3(2x-1)^3-1^2020=5.4^2`
`=>3(2x-1)^3-1=5.16=80`
`=>3(2x-1)^3=81`
`=>(2x-1)^3=27=3^3`
`=>2x-1=3`
`=>2x=4`
`=>x=2`
Vậy `x=2`.
`18)18+|x+7|=9-(-11)`
`=>18+|x+7|=9+11=20`
`=>|x+7|=20-18=2`
`=>` \(\left[ \begin{array}{l}x+7=2\\x+7=-2\end{array} \right.\)
`=>` \(\left[ \begin{array}{l}x=-5\\x=-9\end{array} \right.\)
Vậy `x=-5` hoặc `=9`.
`19)-x+5=3x+(-11)`
`=>-x+5=3x-11`
`=>3x+x=5+11`
`=>4x=16`
`=>x=4`
Vậy `x=4`.
`20)2x+5+(x-7)=(-3)+22`
`=>2x+5+x-7=-3+22`
`=>3x-2=19`
`=>3x=21`
`=>x=7`
Vậy `x=7`
`21)(x+4)(1+|x-2|)=0`
Vì `|x-2|>=0`
`=>|x-2|+1>=1>0`
`=>x+4=0`
`=>x=-4`
Vậy `x=-4`.
`22)2(x-3)-3^2=3(x+1)+2`
`=>2x-6-9=3x+3+2`
`=>2x-15=3x+5`
`=>x=-20`
Vậy `x=-20`.
`23)(x-1)+(x-2)+....+(x-20)=150`
`=>(x+x+....+x)-(1+2+...+20)=150`
`=>20x-(21.20)/2=150`
`=>20x-210=150`
`=>20x=360`
`=>x=18`
Vậy `x=18`.
`24)(98-x)+(96-x)+....+(2-x)=2205`
`=>(98+96+...+2)-(x+x+.....+x)=2205`
`=>(49.100)/2-49x=2205`
`=>49.50-49x=2205`
`=>2450-49x=2205`
`=>49x=245`
`=>x=5`.
Vậy `x=5.`
Hãy giúp mọi người biết câu trả lời này thế nào?
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11612
Anh ơi xem lại câu `15` ạ a đổi `2^4` sai rồi ạ. :))
4027
3515
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