a,x-7=-5
b,128-3.(x+4)=23
d,x-[42+(-28)]=-8
các cậu giúp mik vs ạ!!mình cần đáp án gấp!cảm ơn trước ạ
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\(A=\frac{\left[\left(25-1\right):1+1\right]\left(25+1\right)}{2}=325.\)
\(B=\frac{\left[\left(51-3\right):2+1\right]\left(51+3\right)}{2}=675\)
\(C=\frac{\left[\left(81-1\right):4+1\right]\left(81+1\right)}{2}=861\)
a: \(x+\dfrac{3}{9}=\dfrac{7}{6}\cdot\dfrac{2}{3}\)
=>\(x+\dfrac{1}{3}=\dfrac{14}{18}=\dfrac{7}{9}\)
=>\(x=\dfrac{7}{9}-\dfrac{1}{3}=\dfrac{7}{9}-\dfrac{3}{9}=\dfrac{4}{9}\)
b: \(x-\dfrac{2}{3}=\dfrac{1}{8}:\dfrac{5}{4}\)
=>\(x-\dfrac{2}{3}=\dfrac{1}{8}\cdot\dfrac{4}{5}=\dfrac{1}{10}\)
=>\(x=\dfrac{1}{10}+\dfrac{2}{3}=\dfrac{3+20}{30}=\dfrac{23}{30}\)
a) \(\dfrac{13}{20}+\dfrac{3}{5}+x=\dfrac{5}{6}\)
\(\Rightarrow\dfrac{5}{4}+x=\dfrac{5}{6}\)
\(\Rightarrow x=\dfrac{5}{6}-\dfrac{5}{4}\)
\(\Rightarrow x=\dfrac{-5}{12}\)
b) \(x+\dfrac{1}{3}=\dfrac{2}{5}-\dfrac{-1}{3}\)
\(\Rightarrow x+\dfrac{1}{3}=\dfrac{11}{15}\)
\(\Rightarrow x=\dfrac{11}{15}-\dfrac{1}{3}\)
\(\Rightarrow x=\dfrac{2}{5}\)
c)\(\dfrac{-5}{8}-x=\dfrac{-3}{20}-\dfrac{-1}{6}\)
\(\dfrac{-5}{8}-x=\dfrac{1}{60}\)
\(\Rightarrow x=\dfrac{-5}{8}-\dfrac{1}{60}\)
\(\Rightarrow x=\dfrac{-77}{120}\)
d) \(\dfrac{3}{5}-x=\dfrac{1}{4}+\dfrac{7}{10}\)
\(\Rightarrow\dfrac{3}{5}-x=\dfrac{19}{20}\)
\(\Rightarrow x=\dfrac{3}{5}-\dfrac{19}{20}\)
\(\Rightarrow x=\dfrac{-7}{20}\)
e) \(\dfrac{-3}{7}-x=\dfrac{4}{5}+\dfrac{-2}{3}\)
\(\Rightarrow\dfrac{-3}{7}-x=\dfrac{2}{15}\)
\(\Rightarrow x=\dfrac{-3}{7}-\dfrac{2}{15}\)
\(\Rightarrow x=\dfrac{-59}{105}\)
g) \(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)
\(\Rightarrow\dfrac{-5}{6}-x=\dfrac{1}{4}\)
\(\Rightarrow x=\dfrac{-5}{6}-\dfrac{1}{4}\)
\(\Rightarrow x=\dfrac{-13}{12}\)
a) (x - 2)(2y - 1) = 10 => 10 ⋮ (x - 2) => (x - 2) ∊ Ư(10) = {-10;-5;-2;-1;1;2;5;10}. Ta có bảng:
x - 2 | -10 | -5 | -2 | -1 | 1 | 2 | 5 | 10 |
2y - 1 | -1 | -2 | -5 | -10 | 10 | 5 | 2 | 1 |
2y | 0 | -1 | -4 | -9 | 11 | 6 | 3 | 2 |
y | 0 | Loại | -2 | Loại | Loại | 3 | Loại | 1 |
x | -8 | -3 | 0 | 1 | 3 | 4 | 7 | 12 |
Kết luận | Thỏa mãn | Loại | Thỏa mãn | Loại | Loại | Thỏa mãn | Loại | Thỏa mãn |
Vậy ta có (x;y) ∊ {(-8;0);(0;-2);(4;3);(12;1)}
b, xy - 3y + x - 3 = 7 => xy - 3y + x = 7 + 3 = 10 => xy + x - 3y = 10 => x(y + 1) - 3y = 10 => x(y + 1) - 3(y + 1) = 10 - 3.1 = 10 - 3 = 7 => (x - 3)(y + 1) = 7. Ta có bảng sau:
x - 3 | -7 | -1 | 1 | 7 |
y + 1 | -1 | -7 | 7 | 1 |
x | -4 | 2 | 4 | 10 |
y | -2 | -8 | 6 | 0 |
Kết luận | Thỏa mãn | Thỏa mãn | Thỏa mãn | Thỏa mãn |
Vậy ta có (x;y) ∊ {(-4;-2);(2;-8);(4;6);(10;0)}
a: \(\dfrac{x}{6}=\dfrac{8}{3}\)
=>\(x=6\cdot\dfrac{8}{3}=\dfrac{6}{3}\cdot8=8\cdot2=16\)
b: \(\dfrac{5}{x}=\dfrac{4}{9}\)
=>\(x=\dfrac{5\cdot9}{4}=\dfrac{45}{4}\)
c: \(\dfrac{x+3}{-4}=\dfrac{5}{20}\)
=>\(x+3=\dfrac{-4\cdot5}{20}=-1\)
=>x=-1-3=-4
d: \(\dfrac{7}{3+4x}=\dfrac{-2}{9}\)
=>\(4x+3=\dfrac{9\cdot7}{-2}=-\dfrac{63}{2}\)
=>\(4x=-\dfrac{63}{2}-3=-\dfrac{69}{2}\)
=>\(x=-\dfrac{69}{8}\)
f: ĐKXĐ: x<>1
\(\dfrac{3}{x-1}=\dfrac{x-1}{27}\)
=>\(\left(x-1\right)^2=3\cdot27=81\)
=>\(\left[{}\begin{matrix}x-1=9\\x-1=-9\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=10\left(nhận\right)\\x=-8\left(nhận\right)\end{matrix}\right.\)
a: =>4/3x=7/9-4/9=1/3
=>x=1/4
b: =>5/2-x=9/14:(-4/7)=-9/8
=>x=5/2+9/8=29/8
c: =>3x+3/4=8/3
=>3x=23/12
hay x=23/36
d: =>-5/6-x=7/12-4/12=3/12=1/4
=>x=-5/6-1/4=-10/12-3/12=-13/12
\(\left(x+2\right)\left(x+3\right)\left(x+4\right)\left(x+5\right)-8=\left(x^2+7x+10\right)\left(x^2+7x+12\right)-8\)
Đặt \(x^2+7x=t\)
\(\left(t+10\right)\left(t+12\right)-8=t^2+22t+120-8\)
\(=t^2+22t+112=\left(t+8\right)\left(t+14\right)\)
Theo cách đặt \(=\left(x^2+7x+8\right)\left(x^2+7x+14\right)\)
a, x - 7 = -5
x = (-5) + 7
x = 2
Vậy x = 2
b, 128 - 3 . (x + 4) = 23
3 . (x + 4) = 128 - 23
3 . (x + 4) = 105
(x + 4) = 105 : 3
(x + 4) = 35
x = 35 - 4
x = 31
Vậy x = 31
c, x - [42 + (-28)] = -8
x - 14 = -8
x = (-8) + 14
x = 6
Vậy x = 6
giải :
a) x - 7 = -5
=> x = ( -5 + 7)
=> x = 2
Vậy x = 2
b) 128 - 3 . ( x + 4 ) = 23
=> 3 . ( x + 4 ) = 128 - 23
=> 3 . ( x + 4 ) = 105
=> x + 4 = 105 : 3
=> x + 4 = 35
=> x = 35 - 4
=> x = 31
Vậy x = 31
c ) x - [ 42 + ( - 28 ) ] = -8
=> x - 14 = -8
=> x = -8 + 14
=> x = 6
Vậy x = 6