Tìm x thuộc Z,biết:
a) 2x + 3x = -150
b) -24x + 7x = 3417
c) -3x + x = -842
d) -7x + 2x = -450
Tìm x thuộc Z để biểu thức có giá trị nguyên
a) A=\(\dfrac{3x+21}{x+4}\)
b) B=\(\dfrac{2x^3-7x^2+7x+5}{2x-1}\)
a)
ĐKXĐ: \(x\ne-4\)
Để A nguyên thì \(3x+21⋮x+4\)
\(\Leftrightarrow3x+12+9⋮x+4\)
mà \(3x+12⋮x+4\)
nên \(9⋮x+4\)
\(\Leftrightarrow x+4\inƯ\left(9\right)\)
\(\Leftrightarrow x+4\in\left\{1;-1;3;-3;9;-9\right\}\)
\(\Leftrightarrow x\in\left\{-3;-5;-1;-7;5;-13\right\}\)(nhận)
Vậy: Để A nguyên thì \(x\in\left\{-3;-5;-1;-7;5;-13\right\}\)
b) ĐKXĐ: \(x\ne\dfrac{1}{2}\)
Để B nguyên thì \(2x^3-7x^2+7x+5⋮2x-1\)
\(\Leftrightarrow2x^3-x^2-6x^2+3x+4x-2+7⋮2x-1\)
\(\Leftrightarrow x^2\left(2x-1\right)-3x\left(2x-1\right)+2\left(2x-1\right)+7⋮2x-1\)
\(\Leftrightarrow\left(2x-1\right)\left(x^2-3x+2\right)+7⋮2x-1\)
mà \(\left(2x-1\right)\left(x^2-3x+2\right)⋮2x-1\)
nên \(7⋮2x-1\)
\(\Leftrightarrow2x-1\inƯ\left(7\right)\)
\(\Leftrightarrow2x-1\in\left\{1;-1;7;-7\right\}\)
\(\Leftrightarrow2x\in\left\{2;0;8;-6\right\}\)
hay \(x\in\left\{1;0;4;-3\right\}\)(nhận)
Vậy: \(x\in\left\{1;0;4;-3\right\}\)
Tìm x thuộc Z để thương có giá trị nguyên:
a/ 3x^3+13x^2-7x+5 : 3x-2
b/ 2x^5+4x^4-7x^3-44 : 2x^2-7
a: \(\Leftrightarrow3x^3-2x^2+15x^2-10x+3x-2+7⋮3x-2\)
\(\Leftrightarrow3x-2\in\left\{1;-1;7;-7\right\}\)
hay \(x\in\left\{3;1\right\}\)
b: \(\Leftrightarrow2x^5-7x^3+4x^4-14x^2+14x^2-49x+49x-44⋮2x^2-7\)
\(\Leftrightarrow2401x^2-1936⋮2x^2-7\)
\(\Leftrightarrow4802x^2-3872⋮2x^2-7\)
\(\Leftrightarrow2x^2-7\inƯ\left(12935\right)\)
\(\Leftrightarrow2x^2-7\in\left\{1;5;13;65;199;995;2587;12935;-1;-5\right\}\)
\(\Leftrightarrow2x^2\in\left\{8;72;2\right\}\)
hay \(x\in\left\{2;-2;6;-6;1;-1\right\}\)
Tìm x biết:
a, 16x² – 9(x + 1)²= 0
b, x2 (x – 1) – 4x2 + 8x – 4 = 0
c, x(2x – 3) – 2(3 – 2x) = 0
d, (x – 3)(x² + 3x + 9) – x(x + 2)(x – 2) = 1
e, 4x² + 4x – 6 = 2
f, 2x² + 7x + 3 = 0
e: ta có: \(4x^2+4x-6=2\)
\(\Leftrightarrow4x^2+4x-8=0\)
\(\Leftrightarrow\left(x+2\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=1\end{matrix}\right.\)
f: Ta có: \(2x^2+7x+3=0\)
\(\Leftrightarrow\left(x+3\right)\left(2x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=-\dfrac{1}{2}\end{matrix}\right.\)
tìm x thuộc z
1)(-3x+2)-(5-3x)=-3
2) 3+x-(3x-1)=6-2x
3) (x-5).(3x+4)=0
4) 7x.(2x-1)=0
5) (3x-1).2x=0
giúp mik với mai mik đi học rùi :((
\(\left(-3x+2\right)-\left(5-3x\right)=-3\)
\(\Rightarrow-3x+2-5+3x=-3\)
\(\Rightarrow-3x+3x=-3+5-2\)
\(\Rightarrow0x=0\Rightarrow x\in Z\)
\(3+x-\left(3x-1\right)=6-2x\)
\(\Rightarrow3+x-3x+1=6-2x\)
\(\Rightarrow x-3x+2x=6-1-3\)
\(\Rightarrow0x=2\left(loại\right)\)
\(\left(x-5\right)\left(3x+4\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-5=0\\3x+4=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=5\\x=-\frac{4}{3}\end{cases}}}\)
\(7x\left(2x-1\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}7x=0\\2x-1=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\frac{1}{2}\end{cases}}}\)
\(\left(3x-1\right)2x=0\)
\(\Leftrightarrow\orbr{\begin{cases}3x-1=0\\2x=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{1}{3}\\x=0\end{cases}}}\)
khó hiểu quá
bạn ghi bằng số luôn đừng ghi phần
\(\left(-3x+2\right)-\left(5-3x\right)=-3\)
\(\Rightarrow-3x+2-5+3x=-3\)
\(\Rightarrow-3=-3\)
\(\forall x\in Z\)
\(3+x-\left(3x-1\right)=6-2x\)
\(\Rightarrow2=6\left(vl\right)\)
\(\left(x-5\right)\left(3x+4\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-5=0\\3x+4=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=5\\x=\frac{4}{3}\end{cases}}\)
\(7x\left(2x-1\right)=0\)
\(\Rightarrow\orbr{\begin{cases}7x=0\\2x-1=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x=\frac{1}{2}\end{cases}}\)
\(\left(3x-1\right)2x=0\)
\(\Rightarrow\orbr{\begin{cases}3x-1=0\\2x=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{1}{3}\\x=0\end{cases}}\)
Tìm x thuộc Z, biết:
a) 3x-1 chia hết cho 2x+1
b) 7x+1 chia hết cho 3x-2
Tìm số tự nhiên x biết:
a) 25 + 7x = 144
b) 33 - 12x = 9
c) 128 - 3(x + 4) = 23
d) 71 + (726 - 3x).5 = 2246
e) 720 : [41 - (2x + 5)] = 40
f) (10 - 4x) + 120 : 8 = 16 + 1
g) x + 9x + 7x + 5x = 2244
h) (x + 1) + (x + 2) + (x + 3) +...+ (x + 100) = 5750
i) 1 + 2 + 3 +...+ x = 500500
j) 51 + 52 + 53 +...+ x = 18825
a: Ta có: \(7x+25=144\)
\(\Leftrightarrow7x=119\)
hay x=17
b: Ta có: \(33-12x=9\)
\(\Leftrightarrow12x=24\)
hay x=2
c: Ta có: \(128-3\left(x+4\right)=23\)
\(\Leftrightarrow3\left(x+4\right)=105\)
\(\Leftrightarrow x+4=35\)
hay x=31
d: Ta có: \(71+\left(726-3x\right)\cdot5=2246\)
\(\Leftrightarrow5\left(726-3x\right)=2175\)
\(\Leftrightarrow726-3x=435\)
\(\Leftrightarrow3x=291\)
hay x=97
e: Ta có: \(720:\left[41-\left(2x+5\right)\right]=40\)
\(\Leftrightarrow41-\left(2x+5\right)=18\)
\(\Leftrightarrow2x+5=23\)
\(\Leftrightarrow2x=18\)
hay x=9
f: Ta có: \(10-4x+120:8=16+1\)
\(\Leftrightarrow4x=17-25=-8\)
hay x=-2
g: Ta có: \(x+9x+7x+5x=2244\)
\(\Leftrightarrow22x=2244\)
hay x=102
h: Ta có: \(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)+...+\left(x+100\right)=5750\)
\(\Leftrightarrow100x+5050=5750\)
\(\Leftrightarrow100x=700\)
hay x=7
1. tìm x :
(x^2 - 1/2x) : 2x-(3x-1)^2 : (3x-1) = 0
2. tìm n thuộc N để phép chia là phép chia hết
a. (14x^5 - 7x^3 + 2x): 7x^n
b. (25x^7y^6 - 10x^5y^4 - 6x^3y^2): (-3x^ny^n)
Tìm x, y, z biết:
a, \(\dfrac{2x+1}{5}=\dfrac{4y-5}{9}=\dfrac{2x+4y-4}{7x}\)
\(x=-\dfrac{1}{2}=-0.5,y=\dfrac{5}{4}=1.25\\x=2,y=\dfrac{7}{2}=3.5\)
tim so nguyen x
(3x+9).(3x-6)=0(2x+15)-25=47-(10-x)30(x=2)-6(x-5)-24x=100/4-3x/=8/2x-5/=13/7x+3/=661) (3x + 9)(3x - 6) = 0
=> \(\orbr{\begin{cases}3x+9=0\\3x-6=0\end{cases}}\)
=> \(\orbr{\begin{cases}3x=-9\\3x=6\end{cases}}\)
=> \(\orbr{\begin{cases}x=-3\\x=2\end{cases}}\)
Vậy ...
b) (2x + 15) - 25 = 47 - (10 - x)
=> 2x - 10 = 37 + x
=> 2x - x = 37 + 10
=> x = 47
3, tương tự
4) |4 - 3x| = 8
=> \(\orbr{\begin{cases}4-3x=8\\4-3x=-8\end{cases}}\)
=> \(\orbr{\begin{cases}3x=-4\\3x=12\end{cases}}\)
=> \(\orbr{\begin{cases}x=-\frac{4}{3}\\x=4\end{cases}}\)
Vì x là số nguyên nên ...
còn lại tương tự