x-1/0,5=18/x-1
giup mik nhanh nha
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\(\left(x+4\right)⋮\left(2x+1\right)\\ \Rightarrow\left(2x+8\right)⋮\left(2x+1\right)\\ \Rightarrow\left(2x+1+7\right)⋮\left(2x+1\right)\)
\(Mà\left(2x+1\right)⋮\left(2x+1\right)\Rightarrow7⋮\left(2x+1\right)\Rightarrow2x+1\inƯ\left(7\right)=\left\{\pm1;\pm7\right\}\Rightarrow x\in\left\{-4;-1;0;3\right\}\)
\(\Leftrightarrow2x+1\in\left\{1;7;-1;-7\right\}\)
hay \(x\in\left\{0;3;-1;-4\right\}\)
\(∘backwin\)
\(a ) ( x + 1 ) + ( x + 2 ) + ( x + 3 ) + ... + ( x + 100 ) = 5750\)
\( ( x + x + x + ... + x ) + ( 1 + 2 + 3 + ... + 100 ) = 5750 \)
\( 100 x + ( 1 + 100 ) ×100 : 2 = 5750\)
\(100 x + 5050 = 5750\)
\( 100 x = 5750 − 5050\)
\(100 x = 700\)
\(x = 700 : 100\)
\(x = 7\)
\(b,\) \(B=\)\(\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+...+\dfrac{1}{2021^2}< \dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{2020}+2021\)
\( B < 1 -\)\(\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{2020}-\dfrac{1}{2021}\)
\(B<1-\)\(\dfrac{1}{2021}\)
\(B<\)\(\dfrac{2020}{2021}\)
\(\dfrac{2020}{2021}< 1\)
\(B<1\)
a) (x+1) +(x+2 ) + ...+(x+100)=5750
= 100x + (1+2+3+...+100) = 5750
=100x + 5050 = 5750
--> 100x = 5750-5050=700
--> x=7
(x - 12) - 15 = (20 - 7) - (18 + x)
vậy x = ?
nhanh giùm mik nha, cám ơn, ai nhanh nhất mik tích nhé !
(x - 12) - 15 = (20 - 7) - (18 + x)
x - 12 - 15 = 13- 18 - x
x - 27 = -5 - x
x +x = -5 +27
2x=22
x=11
3.75 : \(\dfrac{1}{4}\) + 3.75 : 0.5 + 3,75 + \(\dfrac{1}{8}\) + 3,75 x 86
= 3,75 : \(\left(\dfrac{1}{4}+0.5+\dfrac{1}{8}\right)\) + 3,75 x 86
= 3,75 : \(\dfrac{7}{8}\) + 322.5
= 4,3 + 322.5 = 326,8
tích hộ chị nha
\(\frac{1}{x^2+9x+20}+\frac{1}{x^2+11x+30}+\frac{1}{x^2+13x+42}=\frac{1}{18}\)
\(\Leftrightarrow\frac{1}{x\left(x+4\right)+5\left(x+4\right)}+\frac{1}{x\left(x+5\right)+6\left(x+5\right)}+\frac{1}{x\left(x+6\right)+7\left(x+6\right)}=\frac{1}{18}\)(điều kiện: \(x\ne\left\{-4;-5;-6;-7\right\}\) )
\(\Leftrightarrow\frac{1}{x+4}-\frac{1}{x+5}+\frac{1}{x+5}-\frac{1}{x+6}+\frac{1}{x+6}-\frac{1}{x+7}=\frac{1}{18}\)
\(\Leftrightarrow\frac{1}{x+4}-\frac{1}{x+7}=\frac{1}{18}\)
\(\Leftrightarrow\frac{3}{\left(x+4\right)\left(x+7\right)}=\frac{1}{18}\)
\(\Rightarrow54=\left(x+4\right)\left(x+7\right)\)
\(\Leftrightarrow x^2+11x-26=0\)
\(\Leftrightarrow x\left(x+13\right)-2\left(x+13\right)=0\Leftrightarrow\left(x+13\right)\left(x-2\right)=0\Leftrightarrow\orbr{\begin{cases}x=-13\\x=2\end{cases}}\)(thỏa mãn ĐKXĐ)
Vậy tập nghiệm của pt là: \(S=\left\{-13;2\right\}\)
Lâu lắm không làm nhể
\(\frac{1}{x^2+9x+20}+\frac{1}{x^2+11x+30}+\frac{1}{x^2+13x+42}=\frac{1}{18}\)
\(\Rightarrow\frac{1}{x^2+4x+5x+20}+\frac{1}{x^2+5x+6x+30}+\frac{1}{x^2+6x+7x+42}=\frac{1}{18}\)
\(\Rightarrow\frac{1}{x.\left(x+4\right)+5.\left(x+4\right)}+\frac{1}{x.\left(x+5\right)+6.\left(x+5\right)}+\frac{1}{x.\left(x+6\right)+7.\left(x+6\right)}=\frac{1}{18}\)
\(\Rightarrow\frac{1}{\left(x+4\right).\left(x+5\right)}+\frac{1}{\left(x+5\right).\left(x+6\right)}+\frac{1}{\left(x+6\right).\left(x+7\right)}=\frac{1}{18}\)
Dùng công thứ \(\frac{1}{x.\left(x+1\right)}=\frac{1}{x}-\frac{1}{x+1}\)
Khi đó \(\frac{1}{x+4}-\frac{1}{x+5}+\frac{1}{x+5}-\frac{1}{x+6}+\frac{1}{x+6}-\frac{1}{x+7}=\frac{1}{18}\)
\(\Rightarrow\frac{1}{x+4}-\frac{1}{x+7}=\frac{1}{18}\)
\(\Rightarrow\frac{x+7}{\left(x+4\right).\left(x+7\right)}-\frac{\left(x+4\right)}{\left(x+4\right).\left(x+7\right)}=\frac{1}{18}\)
\(\Rightarrow\frac{3}{\left(x+4\right).\left(x+7\right)}=\frac{1}{18}\Rightarrow\left(x+4\right).\left(x+7\right)=54\)
\(\Rightarrow\hept{\begin{cases}x+4=6\\x+7=9\end{cases}}\)hoặc \(\hept{\begin{cases}x+4=-6\\x+7=-9\end{cases}}\)
Suy ra \(x=3\)hoặc \(x=-3\)
\(\left(4\frac{46}{65}+x\right).1\frac{1}{12}=5,75\)
\(\Rightarrow\frac{306}{65}+x.\frac{13}{12}=\frac{23}{4}\)
\(\Rightarrow\frac{51}{10}+\frac{13}{12}x=\frac{23}{4}\)
\(\Rightarrow306x=65x=345\)
\(\Rightarrow65x=39\)
\(\Rightarrow x=\frac{3}{5}\)
b, \(\frac{5}{4}-\left(\frac{3}{2}x+0,5\right)=1\frac{1}{4}\)
\(\Rightarrow\frac{5}{4}-\frac{3}{2}x-0,5=\frac{5}{4}\)
\(\Rightarrow\frac{5}{4}-\frac{3}{2}x-\frac{1}{2}=\frac{5}{4}\)
\(\Rightarrow\frac{3}{4}-\frac{3}{2}x=\frac{5}{4}\)
\(\Rightarrow3-6x=5\)
\(\Rightarrow-6x=2\)
\(\Rightarrow x=-\frac{1}{3}\)
Phần b) chị sai nhé ! Dấu [ ] là phần nguyên nâng cao của lớp 6 nhé.
27x18+72x16-41x18
=3x9x9x2 +9x8x8x2 +41x9x2
=9x2x(3x9+8x8-41)
=18x(27+64-41)
=18x50
=900
chúc bn học tốt
18 x y- y : 0,125 +y x 0,5 - 2 x y x 0,15 =18
18 x y - y x 8 + y x 0,5 - y x 0,3 =18
y x (18-8+0,5-0,3)=18
y x 10,2=18
y= \(\frac{30}{17}\)
\(18\times y-y:0,125+y\times0,5-2\times y\times0,15=18\)
\(\Rightarrow18\times y-y\times8+y\times\frac{5}{10}-2\times y\times0,15=18\)
\(\Rightarrow18\times y-y\times8+y\times\frac{1}{2}-2\times y\times\frac{15}{10}=18\)
\(\Rightarrow18\times y-y\times8+y\times2-2\times y\times\frac{3}{2}=18\)
Tự tìm nhé