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1 tháng 11 2017
\(1,x^2+2xy+x+2y\)
\(=\left(x^2+2xy\right)+\left(x+2y\right)\)
\(=x\left(x+2y\right)+\left(x+2y\right)\)
\(=\left(x+2y\right)\left(x+1\right)\)
\(2,x^2-10x+25\)
\(=x^2-2.x.5+5^2\)
\(=\left(x-5\right)^2\)
Đợi mk chút ,mk có việc bận ,tối mk làm tiếp nha bn
1 tháng 11 2017
\(3,x^3+3x^2+3x+1\)
\(=\left(x^3+1\right)+\left(3x^2+3x\right)\)
\(=\left(x+1\right)\left(x^2-x+1\right)+3x\left(x+1\right)\)
\(=\left(x+1\right)\left(x^2-x+1+3x\right)\)
\(=\left(x+1\right)\left(x^2+2x+1\right)\)
\(=\left(x+1\right)\left(x+1\right)^2\)
\(=\left(x+1\right)^3\)
\(4,x^3-8\)
\(=x^3-2^3\)
\(=\left(x-2\right)\left(x^2+2x+4\right)\)
\(5,x^3+27\)
\(=x^3+3^3\)
\(=\left(x+3\right)\left(x^2-3x+9\right)\)
\(6,x^3-\dfrac{1}{8}\)
\(=x^3-\left(\dfrac{1}{2}\right)^3\)
\(=\left(x-\dfrac{1}{2}\right)\left(x^2+\dfrac{1}{2}x+\dfrac{1}{4}\right)\)
\(7,x^3-x+y^3-y\)
\(=\left(x^3+y^3\right)-\left(x+y\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2\right)-\left(x+y\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2-1\right)\)
\(8,4x^2-1\)
\(=\left(2x\right)^2-1^2\)
\(=\left(2x-1\right)\left(2x+1\right)\)
\(9,49x^2-9\)
\(=\left(7x\right)^2-3^2\)
\(=\left(7x-3\right)\left(7x+3\right)\)
PQ
3 tháng 11 2016
x=11 suy ra 12=x+1 thay vào A ta có:
A=x^17- (x+1)x^16 + (x+1)x^15 - (x+1)x^14 + .....- (x+1)x^2+(x+1)x -1
= x^17 - x^17 -x^16 + x^16 + x^15 - x^15 - x^14 +.....- x^3 -x^2 + x^2 +x -1
= x-1= 11-1=10
D
11 tháng 9 2018
\(\left(1+2\right),y^2-13y+12=y^2-12y-y-12=y\left(y-12\right)+\left(y-12\right)=\left(y+1\right)\left(y-12\right)\)
\(3,x^2-x-30=x^2-6x+5x-30=x\left(x-6\right)+5\left(x-6\right)=\left(x+5\right)\left(x-6\right)\)
\(4,y^2+y-42=y^2-6y+7y-42=y\left(y-6\right)+7\left(y-6\right)=\left(y+7\right)\left(y-6\right)\)
\(5,x^2+3x-10=x^2-2x+5x-10=x\left(x-2\right)+5\left(x-2\right)=\left(x+5\right)\left(x-2\right)\)
\(6,x^2-8x+15=x^2-5x-3x+15=x\left(x-5\right)-3\left(x-5\right)=\left(x-3\right)\left(x-5\right)\)
NH
2
19 tháng 10 2015
Ta có x = 7 => x+1=8
Vậy x15-(x+1)14+(x+1)x13-(x+1)x12+...-(x+1)x2+(x+1)x-5
= x15-x15-x14+x14+x13-x13-x12+...-x3-x2+x2+x-5
= 7-5
= 2
19 tháng 3 2020
a) 13 - 2x = x- 2 b)2x-15+8x=7-2x+14 c)12-4y+3y=4y-10-8y
<=>13 + 2 = x+2x <=>2x +2x+8x =7+14+15 <=>12+10 =4y-8y+4y-3y
<=> 15 =3x <=>12x =36 <=> 22 =-3y
<=> x=5 <=>x=3 <=>y=-22/3
vậy S=[5] vậy S=[3] vậy S=[-22/3]
4 tháng 2 2017
Phương trình 1:
\(\frac{x-85}{15}+\frac{x-74}{13}+\frac{x-67}{11}+\frac{x-64}{9}=10\)
\(\Rightarrow\frac{x-85}{15}+\frac{x-74}{13}+\frac{x-67}{11}+\frac{x-64}{9}-10=0\)
\(\Rightarrow\left(\frac{x-85}{15}-1\right)+\left(\frac{x-74}{13}-2\right)+\left(\frac{x-67}{11}-3\right)+\left(\frac{x-64}{9}-4\right)=0\)
\(\Rightarrow\frac{x-85-15}{15}+\frac{x-74-26}{13}+\frac{x-67-33}{11}+\frac{x-64-36}{9}=0\)
\(\Rightarrow\frac{x-100}{15}+\frac{x-100}{13}+\frac{x-100}{11}+\frac{x-100}{9}=0\)
\(\Rightarrow\left(x-100\right)\left(\frac{1}{15}+\frac{1}{13}+\frac{1}{11}+\frac{1}{9}\right)=0\)
Do \(\frac{1}{15}+\frac{1}{13}+\frac{1}{11}+\frac{1}{9}\ne0\)
\(\Rightarrow x-100=0\)
\(\Rightarrow x=100\)
Vậy x = 100.
4 tháng 2 2017
Phương trình 3:
\(\frac{1909-x}{91}+\frac{1907-x}{93}+\frac{1905-x}{95}+\frac{1903-x}{97}+4=0\)
\(\Rightarrow\left(\frac{1909-x}{91}+1\right)+\left(\frac{1907-x}{93}+1\right)+\left(\frac{1905-x}{95}+1\right)+\left(\frac{1903-x}{97}+1\right)=0\)
\(\Rightarrow\frac{1909-x+91}{91}+\frac{1907-x+93}{93}+\frac{1905-x+95}{95}+\frac{1903-x+97}{97}=0\)
\(\Rightarrow\frac{2000-x}{91}+\frac{2000-x}{93}+\frac{2000-x}{95}+\frac{2000-x}{97}=0\)
\(\Rightarrow\left(2000-x\right)\left(\frac{1}{91}+\frac{1}{93}+\frac{1}{95}+\frac{1}{97}\right)=0\)
Do \(\frac{1}{91}+\frac{1}{93}+\frac{1}{95}+\frac{1}{97}\ne0\)
\(\Rightarrow2000-x=0\)
\(\Rightarrow x=2000\)
Vậy x = 2000.
NV
2
18 tháng 10 2015
Ta có x = 7 => x+1=8
Vậy x15-(x+1)14+(x+1)x13-(x+1)x12+...-(x+1)x2+(x+1)x-5
=x15-x15-x14+x14+x13-x13-x12+...-x3-x2+x2+x-5
=7-5
=2
x + 12 = 2
x = 2 - 12
x = -10
x + (-13) = -17 - 15 - x - 8
x - 13 = - 40 - x
x + x = -40 + 13
2x = -27
x = -27/2