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(x- 38) : 16= 12
x-38= 12 . 16
x- 38= 192
x= 192 +38
x= 230
x= 200
5:
a: Số đoạn thẳng tạo thành là: 100*99/2=4950(đoạn)
b: \(B=\left(1-\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)\cdot...\cdot\left(1-\dfrac{1}{2022}\right)\left(1+\dfrac{1}{2}\right)\cdot\left(1+\dfrac{1}{3}\right)\cdot...\cdot\left(1+\dfrac{1}{2022}\right)\)
\(=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot...\cdot\dfrac{2021}{2022}\cdot\dfrac{3}{2}\cdot\dfrac{4}{3}\cdot...\cdot\dfrac{2023}{2022}\)
=1/2022*2023/2
=2023/4044
Barack mới tự học toán 6 hơn 1 tuần, có cách giải này
= 102 + 10 + 112 + 11 + 122 + 12 + 132 + 13 + 142 + 14 + 152 + 15 +162 +16 +172 +17 + 182 + 18 + 192 +19
= 102 + 112 + 132 + 142 + 152 + 162 + 172 + 182 +192 + 10 + 11 +12 +13 + 14 + 15 + 16 +17 + 18 + 19
=[1+(-2)]+[3+(-4)]+...+[19+(-20)] (10 nhóm)
= (-1) + (-1) +....+ (-1) (10 số )
= (-1) . 10
= -10
h: \(\left(-145\right)-5\left(2x-1\right)^3=480\)
=>\(5\left(2x-1\right)^3=-145-480\)=-625
=>(2x-1)3=-125
=>2x-1=-5
=>2x=-5+1=-4
=>x=-4/2=-2
k: \(3\left(-4+x\right)^3-\left(-4\right)^2=-97\)
=>\(3\left(x-4\right)^3-16=-97\)
=>\(3\cdot\left(x-4\right)^3=-97+16=-81\)
=>\(\left(x-4\right)^3=-27\)
=>x-4=-3
=>x=-3+4=1
n: \(195+3\left(-2x+5\right)^3=192\)
=>\(3\left(-2x+5\right)^3=192-195=-3\)
=>\(\left(-2x+5\right)^3=-1\)
=>-2x+5=-1
=>-2x=-1-5=-6
=>\(x=\dfrac{-6}{-2}=3\)
o: \(\left(-148\right)-5\left(-x+6\right)^4=-228\)
=>\(148+5\left(x-6\right)^4=228\)
=>\(5\left(x-6\right)^4=80\)
=>\(\left(x-6\right)^4=16\)
=>\(\left[{}\begin{matrix}x-6=2\\x-6=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=4\end{matrix}\right.\)
p: \(-43-\left(-4+x\right)^4=-44\)
=>\(\left(x-4\right)^4+43=44\)
=>\(\left(x-4\right)^4=1\)
=>\(\left[{}\begin{matrix}x-4=1\\x-4=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=3\end{matrix}\right.\)
q: \(3\left(-x+5\right)^2-\left(-5\right)^2\cdot\left(-2\right)^3=203\)
=>\(3\left(x-5\right)^2-25\cdot\left(-8\right)=203\)
=>\(3\left(x-5\right)^2+200=203\)
=>\(3\left(x-5\right)^2=3\)
=>(x-5)2=1
=>\(\left[{}\begin{matrix}x-5=1\\x-5=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6\\x=4\end{matrix}\right.\)
h.
$(-145)-5(2x-1)^3=480$
$5(2x-1)^3=-145-480=-625$
$(2x-1)^3=-625:5=-125=(-5)^3$
$\Rightarrow 2x-1=-5$
$\Rightarrow x=-3$
k.
$3(-4+x)^3-(-4)^2=-97$
$3(-4+x)^3-16=-97$
$3(-4+x)^3=-97+16=-81$
$(-4+x)^3=-81:3=-27=(-3)^3$
$\Rightarrow -4+x=-3$
$\Rightarrow x=-3-(-4)=1$
1) (-5)+(-18)-(+9)+(-3)
= -23 - 6
= -29
2) (-4)-(-8)+(-15)+(-10)
= 4+ -25
=-21
\(\left(1+\dfrac{1}{1}\right).\left(1+\dfrac{1}{2}\right).\left(1+\dfrac{1}{3}\right).\left(1+\dfrac{1}{4}\right).\left(1+\dfrac{1}{5}\right).\left(1+\dfrac{1}{6}\right)\)
=\(\dfrac{2}{1}.\dfrac{3}{2}.\dfrac{4}{3}.\dfrac{5}{4}.\dfrac{6}{5}.\dfrac{7}{6}=7\)
- Chọn câu D :)
316 - ( 5\(^2\) . 2\(^2\) + 2\(^4\) ) : 2\(^3\) - 3. 2\(^3\)
= 316 - ( 25 . 4 + 16 ) : 8 - 3. 8
= 316 - ( 100 + 16 ) : 8 - 3. 8
= 316 - 116 : 8 - 3. 8
= 200 : 8 - 3. 8
= 25 - 24
= 1
316 - ( 52 . 22 + 24 ) : 23 - 3. 23
= 316 - ( 25 . 4 + 16 ) : 8 - 3. 8
= 316 - ( 100 + 16 ) : 8 - 3. 8
= 316 - 116 : 8 - 3. 8
= 200 : 8 - 3. 8
= 25 - 24
= 1