1. phân tích đa thức thành nhân tử:
a, x^2 - x - 121
b, 81x^2 + 4
2. Tìm GTNN của A biết A=x^2 - 4x + 1
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Những câu hỏi liên quan
17 tháng 10 2021
\(a,=\left(3x-11\right)\left(3x+11\right)\\ b,=\left(3x+1-x+2\right)\left(3x+1+x-2\right)\\ =\left(2x+3\right)\left(4x-1\right)\\ c,=\left(2x+1-8\right)\left(2x+1+8\right)=\left(2x-7\right)\left(2x+9\right)\)
NM
1
TL
4 tháng 9 2021
a, \(6x^3y^2.\left(2-x\right)+9x^2y^2\left(x-2\right)\)
\(=6x^3y^2.\left(2-x\right)-9x^2y^2\left(2-x\right)\)
\(=y^2.\left(2-x\right)\left(6x^3-9x^2\right)\)
\(=3x^2y^2.\left(2-x\right)\left(2x-3\right)\)
b. \(x^2-4x+4y-y^2\)
\(=\left(x^2-y^2\right)-\left(4x-4y\right)\)
\(=\left(x-y\right)\left(x+y\right)-4\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y-4\right)\)
KV
17 tháng 12 2023
a) x³y + x - y - 1
= (x³y - y) + (x - 1)
= y(x³ - 1) + (x - 1)
= y(x - 1)(x² + x + 1) + (x - 1)
= (x - 1)[y(x² + x + 1) + 1]
= (x - 1)(x²y + xy + y + 1)
b) x²(x - 2) + 4(2 - x)
= x²(x - 2) - 4(x - 2)
= (x - 2)(x² - 4)
= (x - 2)(x - 2)(x + 2)
= (x - 2)²(x + 2)
c) x³ - x² - 20x
= x(x² - x - 20)
= x(x² + 4x - 5x - 20)
= x[(x² + 4x) - (5x + 20)]
= x[x(x + 4) - 5(x + 4)]
= x(x + 4)(x - 5)
d) (x² + 1)² - (x + 1)²
= (x² + 1 - x - 1)(x² + 1 + x + 1)
= (x² - x)(x² + x + 2)
= x(x - 1)(x² + x + 2)
KV
17 tháng 12 2023
e) 6x² - 7x + 2
= 6x² - 3x - 4x + 2
= (6x² - 3x) - (4x - 2)
= 3x(2x - 1) - 2(2x - 1)
= (2x - 1)(3x - 2)
f) x⁴ + 8x² + 12
= x⁴ + 2x² + 6x² + 12
= (x⁴ + 2x²) + (6x² + 12)
= x²(x² + 2) + 6(x² + 2)
= (x² + 2)(x² + 6)
g) (x³ + x + 1)(x³ + x) - 2
Đặt u = x³ + x
x³ + x + 1 = u + 1
(u + 1).u - 2
= u² + u - 2
= u² - u + 2u - 2
= (u² - u) + (2u - 2)
= u(u - 1) + 2(u - 1)
= (u - 1)(u + 2)
= (x³ + x - 1)(x³ + x + 2)
= (x³ + x - 1)(x³ + x² - x² - x + 2x + 2)
= (x³ + x - 1)[(x³ + x²) - (x² + x) + (2x + 2)]
= (x³ + x - 1)[x²(x + 1) - x(x + 1) + 2(x + 1)]
= (x³ + x - 1)(x - 1)(x² - x + 2)
h) (x + 1)(x + 2)(x + 3)(x + 4) - 1
= [(x + 1)(x + 4)][(x + 2)(x + 3)] - 1
= (x² + 5x + 4)(x² + 5x + 6) - 1 (1)
Đặt u = x² + 5x + 4
u + 2 = x² + 5x + 6
(1) u.(u + 2) - 1
= u² + 2u - 1
= u² + 2u + 1 - 2
= (u² + 2u + 1) - 2
= (u + 1)² - 2
= (u + 1 + √2)(u + 1 - √2)
= (x² + 5x + 4 + 1 + √2)(x² + 5x + 4 + 1 - √2)
= (x² + 5x + 5 + √2)(x² + 5x + 5 - √2)
29 tháng 12 2020
Câu 1:
Phần a đề sai nên mk sửa lại:
a, x2 + 5x - 14 = x2 - 2x + 7x - 14 = x(x - 2) + 7(x - 2) = (x - 2)(x + 7)
b, xz + yz - 5(x + y) = z(x + y) - 5(x + y) = (x + y)(z - 5)
Câu 2:
x2 - 4x = -4
\(\Leftrightarrow\) x2 - 4x + 4 = 0
\(\Leftrightarrow\) (x - 2)2 = 0
\(\Leftrightarrow\) x - 2 = 0
\(\Leftrightarrow\) x = 2
Vậy x = 2
Chúc bn học tốt!
AD
1
TA
21 tháng 12 2020
a) \(x^2 (x+1)-2x(x+1)+x+1 \\ =(x+1)(x^2-2x+1)\\=(x+1)(x-1)^2\)
b) \(4x^2 -8x+3 \\= (2x^2)-2.2x .2 + 2^2 -1 \\=(2x-2)^2-1^2\\=(2x-2+1)(2x-2-1)\\= (2x-1)(2x-3)\)
12 tháng 10 2021
a) Sửa đề: \(a^2x+a^2y-7x-7y\)
\(=a^2\left(x+y\right)-7\left(x+y\right)=\left(x+y\right)\left(a^2-7\right)\)
b) \(=\left(2x-3y\right)\left(2x+3y\right)+2\left(2x-3y\right)=\left(2x-3y\right)\left(2x+3y+2\right)\)
12 tháng 10 2021
\(c,Sửa:x^2-2x+2y-y^2=\left(x-y\right)\left(x+y\right)-2\left(x-y\right)=\left(x-y\right)\left(x+y-2\right)\\ d,=\left(4x^4+36x^2+81\right)-36x^2\\ =\left(2x^2+9\right)^2-36x^2=\left(2x^2-6x+9\right)\left(2x^2+6x+9\right)\\ e,=x^7+x^6-x^6+x^5-x^5+x^4-x^4+x^3-x^3+x^2-x^2+x^2+x-x+1\\ =x^5\left(x^2+x+1\right)-x^4\left(x^2+x+1\right)+x^2\left(x^2+x+1\right)-x\left(x^2+x+1\right)+\left(x^2+x+1\right)\\ =\left(x^2+x+1\right)\left(x^5-x^4+x^2-x+1\right)\)
SO
2
NV
Nguyễn Việt Lâm
Giáo viên
16 tháng 7 2021
a.
\(=\left(x+1\right)^3-\left(3z\right)^3\)
\(=\left(x+1+3z\right)\left[\left(x+1\right)^2+3z\left(x+1\right)+9z^2\right]\)
\(=\left(x+3z+1\right)\left(x^2+2x+1+3zx+3z+9z^2\right)\)
b.
\(=\left(x-y\right)^2-z\left(x-y\right)\)
\(=\left(x-y\right)\left(x-y-z\right)\)
c.
\(=x^4-1+4x^2-4\)
\(=\left(x^2-1\right)\left(x^2+1\right)+4\left(x^2-1\right)\)
\(=\left(x^2-1\right)\left(x^2+5\right)\)
\(=\left(x-1\right)\left(x+1\right)\left(x^2+5\right)\)
16 tháng 7 2021
a) Ta có: \(x^3+3x^2+3x+1-27z^3\)
\(=\left(x+1\right)^3-\left(3z\right)^3\)
\(=\left(x+1-3z\right)\left(x^2+2x+1+3xz+3z+9z^2\right)\)
b) Ta có: \(x^2-2xy+y^2-zx+yz\)
\(=\left(x-y\right)^2-z\left(x-y\right)\)
\(=\left(x-y\right)\left(x-y-z\right)\)
c) Ta có: \(x^4+4x^2-5\)
\(=x^4+4x^2+4-9\)
\(=\left(x^2+2\right)^2-3^2\)
\(=\left(x^2-1\right)\left(x^2+5\right)\)
\(=\left(x-1\right)\left(x+1\right)\left(x^2+5\right)\)
29 tháng 7 2023
a: =(x^2+x)^2+3(x^2+x)-10
=(x^2+x+5)(x^2+x-2)
=(x^2+x+5)(x+2)(x-1)
b: (x^2+2x)^2-2(x^2+2x)-3
=(x^2+2x-3)(x^2+2x+1)
=(x+1)^2*(x+3)(x-1)
c: =(x^2+x)^2+4(x^2+x)-12
=(x^2+x+6)(x^2+x-2)
=(x^2+x+6)(x+2)(x-1)
d: =(x^2+10x+16)(x^2+10x+24)+16
=(x^2+10x)^2+40(x^2+10x)+400
=(x^2+10x+20)^2
4 tháng 1
Câu 1:
a: Sửa đề: \(A=\left(x+2\right)\left(x^2-2x+4\right)+x\left(1-x\right)\left(1+x\right)\)
\(=x^3+2^3+x\left(1-x^2\right)\)
\(=x^3+8+x-x^3\)
=x+8
b: Khi x=-4 thì A=-4+8=4
c: Đặt A=-2
=>x+8=-2
=>x=-10
Câu 2:
a: \(x^3-3x^2=x^2\cdot x-x^2\cdot3=x^2\left(x-3\right)\)
b: \(5x^3+10x^2+5x\)
\(=5x\cdot x^2+5x\cdot2x+5x\cdot1\)
\(=5x\left(x^2+2x+1\right)\)
\(=5x\left(x+1\right)^2\)
1. \(x^2-x+\frac{1}{4}-\frac{485}{4}=\left(x-\frac{1}{2}\right)^2-\frac{485}{4}=\left(x-\frac{1}{2}-\frac{\sqrt{485}}{2}\right)\left(x-\frac{1}{2}+\frac{\sqrt{485}}{2}\right)=\left(x-\frac{1+\sqrt{485}}{2}\right)\left(x+\frac{\sqrt{485}-1}{2}\right)\)
2) \(81x^2+4=4\left(\frac{81}{4}x^2+1\right)\)
3) \(A=x^2-4x+1=x^2-4x+4-3=\left(x-2\right)^2-3\ge-3\)=> Min A =-3 <=> x=2
. Nhớ L I K E
1.
\(a,x^2-x-121\)\(=\left(x^2-2.x.\frac{1}{2}+\frac{1}{4}\right)-\frac{485}{4}\)\(=\left(x-\frac{1}{2}\right)^2-\frac{485}{4}\)\(=\left(x-\frac{1}{2}-\frac{\sqrt{485}}{2}\right)\left(x-\frac{1}{2}+\frac{\sqrt{485}}{2}\right)\)
\(b,81x^2+4\)\(=\left(9x^2\right)^2+2^2=\left[\left(9x^2\right)^2+36x^2+2^2\right]-36x^2\)
\(=\left(9x^2+2\right)^2-\left(6x\right)^2\)\(=\left(9x^2+2-6x\right)\left(9x^2+2+6x\right)\)
2.
\(A=x^2-4x+1=\left(x^2-2.x.2+4\right)-3\)\(=\left(x-2\right)^2-3\)
Vì \(\left(x-2\right)^2\ge0\)\(\Rightarrow\left(x-2\right)^2-3\ge-3\)
Dấu ''='' xảy ra khi x-2=0 => x=2
Vậy GTNN của A là A=-3 khi x=2