a)187+(921-(921+887))
b)47.75+25.47-5 mũ 2 nhân5
c)100-(150-(-44)+(-22)
Tìm x:
a) 3 mũ x+2 + 3 mũ x+3
44.179+20 mũ 2 -79.44
3.4 mũ 2 :[500-(7.35+125)]
187+[921-(921+887)]
giúp mik nhé mik đg cần gấp
\(44.179+20^2-79.44\\ =44\left(179-79\right)+400\\ =44.100+400\\ =100\left(44+4\right)=4800\\ 3.4^2:\left[500-\left(7.35+125\right)\right]\\ =3.16:\left[500-370\right]\\ =48:130=\dfrac{24}{65}\\ 187+\left[921-\left(921+887\right)\right]\\ =187+921-921-887\\ =187-887=-700\)
44. 179+ 202 - 79.44 3. 42 : [500- (7.35+125)]
= 44. 179+400 - 79.44 = 3. 16: [500- (245+125)]
= 44. (179-79) +400 = 48: [ 500-370 ]
= 44. 100+400 = 48:130
= 4400+400 = 0, 369...
= 4800
187+ [ 921-( 921+887) = 187+ [921- 1808]
= 187+ (-159)
= 28
\(a)44.179+20^2-79.44\)
\(=44.\left(179-79\right)+20^2\)
\(=44.100+400\)
\(=4400+400=4800\)
\(b)3.4^2:\left[500-\left(7.35+125\right)\right]\)
\(=3.4^2:\left[500-\left(245+125\right)\right]\)
\(=3.4^2:\left[500-370\right]\)
\(=3.16:130\)
\(=48:130=\dfrac{24}{65}\)
\(c)187+\left[921-\left(921+887\right)\right]\)
\(=187+\left[921-1808\right]\)
\(=187+\left[921-1808\right]\)
\(=187+\left(-887\right)\)
\(=-700\)
Bài 1: Chứng minh :
a) a / 3.a+ b = c / 3. c + d
b) ( a -b ) mũ 2 / ( c-d ) mũ 2 = a.b / c.d
Bài 2: Tìm x, y, z biết :
a) x : y: z = 3: 5 : 7 và 2x + y + z = 36
b) x / 2 =y /3 ; y / 5 = z / 7 và c+ y +z = 921
Các bạn giúp mình nhé !
Bài 1:Thêm đề: Cho tỉ lệ thức \(\dfrac{a}{b}=\dfrac{c}{d}\)
a, \(\dfrac{a}{3a+b}=\dfrac{c}{3c+d}\)
Đặt \(\dfrac{a}{b}=\dfrac{c}{d}=k\Rightarrow\left\{{}\begin{matrix}a=bk\\c=dk\end{matrix}\right.\)
Ta có:
\(\left\{{}\begin{matrix}\dfrac{bk}{3bk+b}=\dfrac{bk}{b\left(3k+1\right)}=\dfrac{k}{3k+1}\\\dfrac{dk}{3dk+d}=\dfrac{dk}{d\left(3k+1\right)}=\dfrac{k}{3k+1}\end{matrix}\right.\)
\(\Rightarrow\dfrac{a}{3a+b}=\dfrac{c}{3c+d}\)
b, \(\dfrac{\left(a-b\right)^2}{\left(c-d\right)^2}=\dfrac{ab}{cd}\)
Ta có: \(\dfrac{a}{b}=\dfrac{c}{d}\Rightarrow\dfrac{a}{c}=\dfrac{b}{d}\)
Đặt \(\dfrac{a}{c}=\dfrac{b}{d}=k\Rightarrow\left\{{}\begin{matrix}a=ck\\b=dk\end{matrix}\right.\)
Ta có: \(\left\{{}\begin{matrix}\dfrac{\left(ck-dk\right)^2}{\left(c-d\right)^2}=\dfrac{c^2k^2-2cdk^2+d^2k^2}{c^2-2cd+d^2}=\dfrac{k^2\left(c^2-2cd+d^2\right)}{c^2-2cd+d^2}=k^2\\\dfrac{ck.dk}{c.d}=k^2\end{matrix}\right.\) \(\Rightarrow\dfrac{\left(a-b\right)^2}{\left(c-d\right)^2}=\dfrac{ab}{cd}\) Chúc bạn học tốt!!!Theo đề ta có:
\(\dfrac{a}{b}=\dfrac{c}{d}=\dfrac{a}{c}=\dfrac{b}{d}\)
Áp dụng tính chất dãy tỉ số bằng nhau:
\(\dfrac{a}{b}=\dfrac{c}{d}=\dfrac{a}{c}=\dfrac{b}{d}=\dfrac{3a}{3c}=\dfrac{b}{d}=\dfrac{3a+b}{3c+d
}\)
\(\Rightarrow\dfrac{a}{c}=\dfrac{3a+b}{3c+d}=\dfrac{a}{3a+b}=\dfrac{c}{3c+d}\left(đpcm\right)\)
b/ Theo đề dã cho, có:
\(\dfrac{a}{b}=\dfrac{c}{d}=\dfrac{a}{c}=\dfrac{b}{d}\)
Áp dụng tính chất dãy tỉ số bằng nhau:
\(\dfrac{a}{b}=\dfrac{c}{d}=\dfrac{a}{c}=\dfrac{b}{d}=\dfrac{a-b}{c-d}=\dfrac{\left(a-b\right)^2}{\left(c-d\right)^2}\)(1)
Ta có: \(\dfrac{a}{b}=\dfrac{c}{d}=\dfrac{ab}{b^2}=\dfrac{cd}{d^2}\left(2\right)\)
Từ (1) và (2)\(\Rightarrow\dfrac{\left(a-b\right)^2}{\left(c-d\right)^2}=\dfrac{ab}{cd}\)(đpcm)
(nhầm :))
Giải rõ ra nhé!Mik đag cực kì gấp
a)4x5 mũ 2 -81 : 3 mũ 2
b) 2 mũ 4 x 5 - [ 131 - ( 13 -4) mũ 2]
c) 3 mũ 3 x 22 x 3 mũ 3 x 19
d)100 : {250:[450-4x5 mũ 3 - 2 mũ 2 x 25]}
Bài 1:
555 - 5 x [ 409 - (2 mũ 3 x 3 - 21) mũ 2 - 310]
Bài 2:
a) 10x +187 = 617 mũ 10 : 617 mũ 9
b) 5 mũ 2 + x = 25 mũ 4
c) (2x + 17) chia hết (x + 4)
help me!
(x - 257) - 921 = 2 mũ 5
mình cần gấp nhé!CẢM ƠN!
\(\left(x-257\right)-921=2^5\)
\(x-257=32+921\)
\(\)\(x-257=953\)
\(x=953+257\)
\(x=1210\)
\(\left(x-257\right)-921=2^5\)
\(\Rightarrow x-1178=32\Rightarrow x=32+1178=1210\)
(x-257)-921=32
(x-257)=32+921
(x-257)=953
x=953+257
x=1210
nhớ tick cho mik nhé !
Bài 1 So sánh
72 mũ 45 -72 mũ 44 và 72 mũ 44- 72 mũ 43
Bài 2
a, cho S = 1 + 2 + 2 mũ 2 + 2 mũ 3 ..............+2 mũ 9
Hãy so sánh với 5 x 2 mũ 8
b, Cho A = 3+3+3 mũ 2+3 mũ 3.......... + 3 mũ 100
Tìm số tự nhiên n , biết rằng 2. A.3 mũ n
Gấp gấp gấp 😧😧😧😧😧😧
So sánh : và \(72^{44}-72^{43}\)
Ta có :
\(72^{45}-72^{44}=72^{44}\left(72-1\right)\)
\(72^{44}-72^{43}=72^{43}\left(72-1\right)\)
Vì 7244 > 7243 => 7244 (72-1) > 7243 (72-1)
hay 7245 -7244 > 7244 - 7243
Bài 2: Tìm x, biết
a) (x+3) mũ 2 - (x-4)(x+8) = 1
b) (x+3)(x mũ 2 - 3x + 9) -x(x-2)(x+2) = 15
c) (x-2) mũ 2 - (x+3) mũ 2 - 4(x+1) = 5
d) (2x-3)(2x+3) - (x-1) mũ 2 - 3x(x-5) = -44
e) (x-2) mũ 3 - (x-3)(x mũ 2 + 3x + 9) + 6(x+1) mũ 2 = 49
f) 5x(x-3) mũ 2 - 5(x-1) mũ 3 + 15(x+2)(x-2) = 5
g) (x+3) mũ 3 - x(3x+1) mũ 2 + (2x+1)(4x mũ 2 - 2x + 1) - 3x mũ 2 = 42
a) \(\left(x+3\right)^2-\left(x-4\right)\left(x+8\right)=1\)
\(\Leftrightarrow\left(x^2+6x+9\right)-\left(x^2+4x-32\right)-1=0\)
\(\Leftrightarrow2x=-40\)
\(\Rightarrow x=-20\)
b) \(\left(x+3\right)\left(x^2-3x+9\right)-x\left(x-2\right)\left(x+2\right)=15\)
\(\Leftrightarrow x^3+27-x^3+4x=15\)
\(\Leftrightarrow4x=-12\)
\(\Rightarrow x=-3\)
c) \(\left(x-2\right)^2-\left(x+3\right)^2-4\left(x+1\right)=5\)
\(\Leftrightarrow\left(x^2-4x+4\right)-\left(x^2+6x+9\right)-\left(4x+4\right)=5\)
\(\Leftrightarrow-14x=14\)
\(\Rightarrow x=-1\)
d) \(\left(2x-3\right)\left(2x+3\right)-\left(x-1\right)^2-3x\left(x-5\right)=-44\)
\(\Leftrightarrow4x^2-9-\left(x^2-2x+1\right)-\left(3x^2-15x\right)=-44\)
\(\Leftrightarrow17x=-34\)
\(\Rightarrow x=-2\)
e) \(\left(x-2\right)^3-\left(x-3\right)\left(x^2+3x+9\right)+6\left(x+1\right)^2=49\)
\(\Leftrightarrow x^3-6x^2+12x-8-x^3+27+6x^2+12x+6=49\)
\(\Leftrightarrow24x=24\)
\(\Rightarrow x=1\)
f) \(5x\left(x-3\right)^2-5\left(x-1\right)^3+15\left(x+2\right)\left(x-2\right)=5\)
\(\Leftrightarrow5x^3-30x^2+45x-5x^3+15x^2-15x+5+15x^2-60=5\)
\(\Leftrightarrow30x=60\)
\(\Rightarrow x=2\)
g) \(\left(x+3\right)^3-x\left(3x+1\right)^2+\left(2x+1\right)\left(4x^2-2x+1\right)-3x^2=42\)
\(\Leftrightarrow x^3+9x^2+27x+27-9x^3-6x^2-x+8x^3+1-3x^2=42\)
\(\Leftrightarrow26x=14\)
\(\Rightarrow x=\frac{7}{13}\)
Bài 4: Tìm x biết
a) (x-3) mũ 2 -4=0
b) (2x+3) mũ 2 - (2x+1)(2x-1)=22
c) (4x+3)(4x-3) - (4x-5) mũ 2=16
d) x mũ 3 - 9x mũ 2 + 27x - 27= -8
e) (x+1) mũ 3 - x mũ 2 nhân (x+3)=2
f) (x-2) mũ 3 - x(x-1)(x+1) + 6x mũ 2=5
a) ( x - 3 )2 - 4 = 0
<=> ( x - 3 )2 - 22 = 0
<=> ( x - 3 - 2 )( x - 3 + 2 ) = 0
<=> ( x - 5 )( x - 1 ) = 0
<=> x = 5 hoặc x = 1
b( 2x + 3 )2 - ( 2x + 1 )( 2x - 1 ) = 22
<=> 4x2 + 12x + 9 - ( 4x2 - 1 ) = 22
<=> 4x2 + 12x + 9 - 4x2 + 1 = 22
<=> 12x + 10 = 22
<=> 12x = 12
<=> x = 1
c) ( 4x + 3 )( 4x - 3 ) - ( 4x - 5 )2 = 16
<=> 16x2 - 9 - ( 16x2 - 40x + 25 ) = 16
<=> 16x2 - 9 - 16x2 + 40x - 25 = 16
<=> 40x - 34 = 16
<=> 40x = 50
<=> x = 50/40 = 5/4
d) x3 - 9x2 + 27x - 27 = -8
<=> ( x - 3 )3 = -8
<=> ( x - 3 )3 = (-2)3
<=> x - 3 = -2
<=> x = 1
e) ( x + 1 )3 - x2( x + 3 ) = 2
<=> x3 + 3x2 + 3x + 1 - x3 - 3x2 = 2
<=> 3x + 1 = 2
<=> 3x = 1
<=> x = 1/3
f) ( x - 2 )3 - x( x - 1 )( x + 1 ) + 6x2 = 5
<=> x3 - 6x2 + 12x - 8 - x( x2 - 1 ) + 6x2 = 5
<=> x3 + 12x - 8 - x3 + x = 5
<=> 13x - 8 = 5
<=> 13x = 13
<=> x = 1
a) \(\left(x-3\right)^2-4=0\)
=> \(\left(x-3\right)^2-2^2=0\)
=> \(\left(x-3-2\right)\left(x-3+2\right)=0\)
=> \(\left(x-5\right)\left(x-1\right)=0\)
=> \(\orbr{\begin{cases}x=5\\x=1\end{cases}}\)
b) \(\left(2x+3\right)^2-\left(2x+1\right)\left(2x-1\right)=22\)
=> \(\left(2x+3\right)^2-\left[\left(2x\right)^2-1^2\right]=22\)
=> \(\left(2x+3\right)^2-\left(4x^2-1\right)=22\)
=> \(\left(2x\right)^2+2\cdot2x\cdot3+3^2-4x^2+1=22\)
=> \(4x^2+12x+9-4x^2+1=22\)
=> \(12x+9+1=22\)
=> \(12x+10=22\)
=> 12x = 12
=> x = 1
c) \(\left(4x+3\right)\left(4x-3\right)-\left(4x-5\right)^2=16\)
=> \(\left(4x\right)^2-3^2-\left[\left(4x\right)^2-2\cdot4x\cdot5+5^2\right]=16\)
=> \(16x^2-9-\left(16x^2-40x+25\right)=16\)
=> \(16x^2-9-16x^2+40x-25=16\)
=> \(-9+40x-25=16\)
=> \(40x=16+25-\left(-9\right)=16+25+9=50\)
=> x = 50/40 = 5/4
d) \(x^3-9x^2+27x-27=-8\)
=> \(x^3-3\cdot x^2\cdot3+3\cdot x\cdot3^2-3^3=8\)
=> \(\left(x-3\right)^3=-8\)
=> \(\left(x-3\right)^3=\left(-2\right)^3\)
=> x - 3 = -2 => x = 1
e) \(\left(x+1\right)^3-x^2\left(x+3\right)=2\)
=> \(x^3+3x^2+3x+1-x^3-3x^2=2\)
=> \(3x+1=2\)
=> \(3x=1\)=> x = 1/3
f) \(\left(x-2\right)^3-x\left(x-1\right)\left(x+1\right)+6x^2=5\)
=> \(x^3-3\cdot x^2\cdot2+3\cdot x\cdot2^2-2^3-x\left(x^2-1\right)+6x^2=5\)
=> \(x^3-6x^2+12x-8-x^3+x+6x^2=5\)
=> \(\left(12x+x\right)-8=5\)
=> 13x = 13
=> x = 1
a) (x+3)^2-4=0
=>(x+3)^2 = 4
=>(x+3)^2 = 2^2 = (-2)^2
=>x+3 = 2 hoặc -2
=> x= -1 hoặc -5
cho x/2=y/3 =z/5 a) x +y+z =30 b) x- 2x +3z=22 c)x. y.z = -240 d) x mũ 2 + 3y mũ 2 - z mũ 2=150