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cậu giải thích giùm mình đoạn này với P(x)=x^7-(x+1)x^6+(x+1)x^5-(x+1)x^4+(x+1)x^3-(x+1)x^2+(x+1)x+15
P(x)=x^7-x^7-x^6+x^6+x^5-x^5-x^4+x^4+x^3-x^3-x^2+x^2+x+15
P(x)=x+15=79+15=94
hay giai giup mk may phan nay nhe
cmr cac bieu thuc sau ko phu thuoc vao x:
c)C=x(x^3+x^2-3x-2)-(x^2-2)(x^2+x-1)
e)E=(x+1)(x^2-x+1)-(x-1)(x^2+x+1)
tinh gia tri cua da thuc
b)Q(x)=x^14-10x^13=10x^12-10x^11+...+10x^2-10x+10 voi x=9
c)R(x)=x^4-17x^3+17x^2_17x+20 või=16
d)S(x)=x^10-13x^9+13x^8-13X^7+...+13x^2-13x+10 voi 12
a. 2(x-1) + (x+2) - (x+3) = 15 - (x+1)
=>2x-2+x+2-x-3=15-x-1
=>(2x+x-x)-2+2-3=15-1-x
=>2x-3=14-x
=>3x=17
=>x=17/3
b. x+1/15 + x+2/14 = x+4/12 + x+5/11
\(\Rightarrow\frac{x+1}{15}+1+\frac{x+2}{14}+1=\frac{x+4}{12}+1+\frac{x+5}{11}+1\)
\(\Rightarrow\frac{x+16}{15}+\frac{x+16}{14}=\frac{x+16}{12}+\frac{x+16}{11}\)
\(\Rightarrow\frac{x+16}{15}+\frac{x+16}{14}-\frac{x+16}{12}-\frac{x+16}{11}=0\)
\(\Rightarrow\left(x+16\right)\left(\frac{1}{15}+\frac{1}{14}-\frac{1}{12}-\frac{1}{11}\right)=0\)
\(\Rightarrow x+16=0\).Do \(\frac{1}{15}+\frac{1}{14}-\frac{1}{12}-\frac{1}{11}\ne0\)
=>x=-16
`a,`\(2^x -15= 2^4+1\)
`-> 2^x-15=17`
`-> 2^x=17+15`
`-> 2^x=32`
`-> 2^x=2^5`
`-> x=5`
`b,` Có phải đề là \(\dfrac{x+1}{65}+\dfrac{x+2}{64}=\dfrac{x+3}{63}+\dfrac{x+4}{62}\) ?
`=>`\(\dfrac{x+1}{65}+1+\dfrac{x+2}{64}+1=\dfrac{x+3}{63}+1+\dfrac{x+4}{62}+1\)
`=>`\(\dfrac{x+1+65}{65}+\dfrac{x+2+64}{64}-\dfrac{x+3+63}{63}-\dfrac{x+4+62}{62}=0\)
`=>`\(\dfrac{x+66}{65}+\dfrac{x+66}{64}-\dfrac{x+66}{63}-\dfrac{x+66}{62}=0\)
`=>`\(\left(x+66\right)\left(\dfrac{1}{65}+\dfrac{1}{64}-\dfrac{1}{63}-\dfrac{1}{62}\right)=0\)
Mà `1/65+1/64-1/63-1/62 \ne 0`
`-> x+66=0`
`-> x=-66`
a: =>2^x=2^4+16=32
=>x=5
b: Sửa đề: \(\dfrac{x+1}{65}+\dfrac{x+2}{64}=\dfrac{x+3}{63}+\dfrac{x+4}{62}\)
=>\(\left(\dfrac{x+1}{65}+1\right)+\left(\dfrac{x+2}{64}+1\right)=\left(\dfrac{x+3}{63}+1\right)+\left(\dfrac{x+4}{62}+1\right)\)
=>x+66=0
=>x=-66
1: x=3/4-1/2=3/4-2/4=1/4
2: x-1/5=2/11
=>x=2/11+1/5=21/55
3: x-5/6=16/42-8/56
=>x-5/6=8/21-4/28=5/21
=>x=5/21+5/6=15/14
4: x/5=5/6-19/30
=>x/5=25/30-19/30=6/30=1/5
=>x=1
5: =>|x|=1/3+1/4=7/12
=>x=7/12 hoặc x=-7/12
6: x=-1/2+3/4
=>x=3/4-1/2=1/4
11: x-(-6/12)=9/48
=>x+1/2=3/16
=>x=3/16-1/2=-5/16
1)x= 1/4
2)x= 2/11+ 1/5
x= 21/55
3)x - 5/6 = 5/21
x = 5/21+5/6
x = 15/14
4)x/5 = 5/6 + -19/30
x:5 = 1/5
x = 1/5.5
x = 1
5) |x| - 1/4 = 6/18
|x| = 6/18 - 1/4
|x| =7/12
⇒x= 7/12 hoặc -7/12
6)x = -1/2 +3/4
x= 1/4
7) x/15 = 3/5 + -2/3
x:15 = -1/15
x = -1/15. 15
x = -1
8)11/8 + 13/6 = 85/x
85/24 = 85/x
⇒ x = 24
9) x - 7/8 = 13/12
x = 13/12 + 7/8
x = 47/24
10)x - -6/15 = 4/27
x = 4/27 + (-6/15)
x = -34/135
11) -(-6/12)+x = 9/48
x= 9/48 - 6/12
x = -5/16
12) x - 4/6 = 5/25 + -7/15
x -4/6 = -4/15
x = -4/15 + 4/6
x = 2/5
a) |x - 2| + |4 + x| = 15
Ta có : x - 2 = 0 => x = 2
4 + x = 0 => x = -4
Ta có bảng xét dấu :
x | -4 2 |
x-2 | - - 0 + |
4+x | - 0 + + |
Từ bảng xét dấu có :
+Nếu x < -4 thì x - 2 < 0 và 4 + x < 0
Do đó : |x - 2| + |4 + x| =15
<=> -(x-2) - (4 + x) = 15
<=> -x + 2 - 4 - x = 15
<=> -x - x - 2 = 15
<=> -2x = 15 + 2 = 17
<=> x = -17/2 (t/m )
+Nếu -4 </ x </ 2 thì x + 2 </ 0 và 4 + x >/ 0
Do đó : |x - 2| + |4 + x| = 15
<=> -(x - 2) - 4 + x = 15
<=> -x + 2 + 4 + x = 15
<=> 0x + 6 = 15
<=> 0x = 9
Ta thấy : không có giá trị nào của x thỏa mãn 0x = 9 Vì 0x = 0 mà 9 khác 0
+Nếu x > 2 thì : x - 2 > 0; 4 + x = 0
Do đó : ... = x - 2 + 4 + x = 15 <=> 2x + 2 = 15 <=> x = 13/2 (t/m)
Vậy x = -17/2 hoặc x = 13/2
a) \(\dfrac{2}{3}\left(x+1\right)-\dfrac{4}{5}\left(x+2\right)=\dfrac{35}{2}\)
\(\Rightarrow\dfrac{2}{3}x+\dfrac{2}{3}-\dfrac{4}{5}x-\dfrac{8}{5}=\dfrac{35}{2}\)
\(\Rightarrow\left(\dfrac{2}{3}-\dfrac{4}{5}\right)x+\left(\dfrac{2}{3}-\dfrac{8}{5}\right)=\dfrac{35}{2}\)
\(\Rightarrow-\dfrac{2}{15}x-\dfrac{14}{15}=\dfrac{35}{2}\)
\(\Rightarrow-\dfrac{2}{15}x=\dfrac{553}{30}\)
\(\Rightarrow x=\dfrac{553}{30}:-\dfrac{2}{15}\)
\(\Rightarrow x=-\dfrac{553}{4}\)
b) \(4\left(x-2\right)+5\left(x+1\right)=-15\)
\(\Rightarrow4x-8+5x+5=-15\)
\(\Rightarrow\left(4+5\right)x+\left(-8+5\right)=-15\)
\(\Rightarrow9x-3=-15\)
\(\Rightarrow9x=-15+3\)
\(\Rightarrow x=\dfrac{-12}{9}\)
\(\Rightarrow x=-\dfrac{4}{3}\)
c) \(\dfrac{3}{2}:x+\left(-\dfrac{5}{2}\right)=-\dfrac{7}{3}\)
\(\Rightarrow\dfrac{3}{2}:x=-\dfrac{7}{3}+\dfrac{5}{2}\)
\(\Rightarrow\dfrac{3}{2}x=\dfrac{1}{6}\)
\(\Rightarrow x=\dfrac{1}{6}:\dfrac{3}{2}\)
\(\Rightarrow x=\dfrac{1}{9}\)
Có x - 2 = 0 <=> x = 2
4 + x = 0 <=> x = -4
Lập bảng xét dấu
+Nếu x < -4 thì x - 2 < 0 và 4+x < 0
=> -(x-2)-(4+x) = 15
<=> -x + 2 - 4 - x = 15
<=> -x - x - 2 =15
<=> -2x = 17
<=> x = -17/2 (t/m)
+Nếu -4 \(\le\)x\(\le\)2 thì x - 2 \(\le\)0 và 4+x \(\ge\)0
=> -(x-2) + 4 + x = 15
<=> -x + 2 + 4 + x = 15
<=> 0x + 6 = 15
<=> 0x = 9
<=> k có x t/m
+ Nếu x > 2 thì x - 2 > 0 và 4 + x > 0
<=> x - 2 + 4 + x = 15
<=> 2x + 2 = 15
<=> 2x = 13
<=> x = 13/2 (t/m)
Vậy..