tính :
a) (x^2 + y/x):(x/y^2-1/y+1/x)
b) (1/x^2+4x+4 - 1/x^2-4x+4):(1/x+2 + 1/x+2)
Rút gọn biểu thức:
a, 3(x-y)^2-2(x-y)^2+(x-y)(x+y)
b, (x-2)(x^2+2x+4)-x(x-2)(x+2)+4x
c, 2(2x+5)^2-3(4x+1)(1-4x)
d, 4x^2-12+9/9-4x^2
e, x^4+x^3+x+1/x^4-x^3+2x^2-x+1
d) \(\frac{4x^2-12x+9}{9-4x^2}=-\frac{\left(2x+3\right)^2}{\left(2x-3\right)\left(2x+3\right)}=\frac{2x+3}{2x-3}\)
4. Tính đạo hàm của các hàm số sau:
a) \(y = (3x^2-4x+1)^{-4}\)
b) \(y = 3^{x^2-1} + e^{-x+1}\)
c) \(y = \ln (x^2-4x) + \log_{3} (2x-1)\)
d) \(y =x . \ln x + 2^{\frac{x-1}{x+1}}\)
e) \(y = x^{-7} - \ln (x^2-1)\)
`a)TXĐ:R\\{1;1/3}`
`y'=[-4(6x-4)]/[(3x^2-4x+1)^5]`
`b)TXĐ:R`
`y'=2x. 3^[x^2-1] ln 3-e^[-x+1]`
`c)TXĐ: (4;+oo)`
`y'=[2x-4]/[x^2-4x]+2/[(2x-1).ln 3]`
`d)TXĐ:(0;+oo)`
`y'=ln x+2/[(x+1)^2].2^[[x-1]/[x+1]].ln 2`
`e)TXĐ:(-oo;-1)uu(1;+oo)`
`y'=-7x^[-8]-[2x]/[x^2-1]`
Lời giải:
a.
$y'=-4(3x^2-4x+1)^{-5}(3x^2-4x+1)'$
$=-4(3x^2-4x+1)^{-5}(6x-4)$
$=-8(3x-2)(3x^2-4x+1)^{-5}$
b.
$y'=(3^{x^2-1})'+(e^{-x+1})'$
$=(x^2-1)'3^{x^2-1}\ln 3 + (-x+1)'e^{-x+1}$
$=2x.3^{x^2-1}.\ln 3 -e^{-x+1}$
c.
$y'=\frac{(x^2-4x)'}{x^2-4x}+\frac{(2x-1)'}{(2x-1)\ln 3}$
$=\frac{2x-4}{x^2-4x}+\frac{2}{(2x-1)\ln 3}$
d.
\(y'=(x\ln x)'+(2^{\frac{x-1}{x+1}})'=x(\ln x)'+x'\ln x+(\frac{x-1}{x+1})'.2^{\frac{x-1}{x+1}}\ln 2\)
\(=x.\frac{1}{x}+\ln x+\frac{2}{(x+1)^2}.2^{\frac{x-1}{x+1}}\ln 2\\ =1+\ln x+\frac{2^{\frac{2x}{x+1}}\ln 2}{(x+1)^2}\)
e.
\(y'=-7x^{-8}-\frac{(x^2-1)'}{x^2-1}=-7x^{-8}-\frac{2x}{x^2-1}\)
làm các phép tính sau
a,y/2x2-xy + 4x/y2-2xy
b,1/x+2 + 3/x2-4 + x-14/(x2+4x+4) (x-2)
c,1/x+2 + 1/(x+2)(4x+7)
d,1/x+3 + 1/(x+3) (x+2) + 1/(x+2)(4x+7)
Rút gọn các biểu thức sau:
a) ((1/x^2+4x+4)-(1/x^2-4x+4)):((1/x+2)+(1/x^2-2))
b)((2x/2x-y)-(4x^2/4x^2+4xy+y^2)):((2x/4x^2-y^2)+(1/y-2x))
a,sửa đề : \(\left(\frac{1}{x^2+4x+4}-\frac{1}{x^2-4x+4}\right):\left(\frac{1}{x+2}+\frac{1}{x^2-4}\right)\)
\(=\left(\frac{1}{\left(x+2\right)^2}-\frac{1}{\left(x-2\right)^2}\right):\left(\frac{x-2+1}{\left(x+2\right)\left(x-2\right)}\right)\)
\(=\left(\frac{x^2-4x+4-x^2-4x-4}{\left(x+2\right)^2\left(x-2\right)^2}\right):\left(\frac{x-1}{\left(x+2\right)\left(x-2\right)}\right)\)
\(=\frac{-8x\left(x+2\right)\left(x-2\right)}{\left(x+2\right)^2\left(x-2\right)^2\left(x-1\right)}=\frac{-8x}{\left(x-1\right)\left(x^2-4\right)}\)
b, \(\left(\frac{2x}{2x-y}-\frac{4x^2}{4x^2+4xy+y^2}\right):\left(\frac{2x}{4x^2-y^2}+\frac{1}{y-2x}\right)\)
\(=\left(\frac{2x}{2x-y}-\frac{4x^2}{\left(2x+y\right)^2}\right):\left(\frac{2x}{\left(2x-y\right)\left(2x+y\right)}-\frac{1}{2x-y}\right)\)
\(=\left(\frac{2x\left(2x+y\right)^2-4x^2\left(2x-y\right)}{\left(2x-y\right)\left(2x+y\right)^2}\right):\left(\frac{2x-\left(2x+y\right)}{\left(2x-y\right)\left(2x+y\right)}\right)\)
\(=\left(\frac{8x^3+8x^2y+2xy^2-8x^3+4x^2y}{\left(2x-y\right)\left(2x+y\right)^2}\right):\left(\frac{-y}{\left(2x-y\right)\left(2x+y\right)}\right)\)
\(=-\left(\frac{12x^2y+xy^2}{2x+y}\right)=\frac{-12x^2y-xy^2}{2x+y}\)
tính gt biểu thức
a)P=(x^3+6x^2+12x+8)+3(x^2+4x+4)y+3(x+2)y^2+y^3 với x+y=8
b)Q=(x-1)^3-4x(x+1)(x-1)+3(x-1)(x^2+x+1) với x=-2
https://olm.vn/hoi-dap/detail/227952918582.html vào link này xem câu a nha Lê Phương Nhung
b)Q = (x - 1)3 - 4x(x + 1)(x - 1) + 3(x - 1)(x2 + x + 1)
Q = (x - 1)3 - 4x(x2 - 1) + 3(x3 - 1)
Thay x = -2 vào Q ta dc :
(-3)3 - 4 . (-2) . 3 + 3 . (-9) = -27 + 24 - 27 = -30
1) Chứng minh bt sau ko phụ thuộc vào biến
a) ( x-1)^ 3 - ( x+4) ( x^2- 4x+16) + 3x ( x-1)
b) (2x+3y) ( 4x^2- 6xy + 9y^2) - ( 2x - 3y ) ( 4x^2+ 6xy + 9y^2) - 27 ( 2y^3- 1 )
c) y( x^2- y^2) ( x^2+ y^2) - y( x^4- y^4)
d) ( x-1)^3- ( x-1) ( x^2+ x + 1 ) - 3 ( 1-x).x
Bài 1: thực hiện phép tính
a, 2xy(x^2 + xy - 3y^2)
b, (x+2)(3x^2 - 4x)
c, (x^3 + 3x^2 - 8x - 20) : (x + 2)
d, (4x^2 - 4x - 4) : (x+4)
e, (2x^3 - 3x^2 + x - 2) : (x + 5)
f, (x+y)^2 + (x-y)^2 - 2(x+y)(x-y)
g, (a+b)^3 - (a-b)^3 - 2b^3
h, (x - y)(x + y)(x^2 + y^2)(x^4 + y^4)
i, 2x^2(x - 2) + 3x(x^2 - x - 2) - 5(3 - x^2)
k, (x - 1)(x - 3) - (4 - x)(2x + 1) - 3x^2 + 2x - 5
l, (x^4 - x^3 - 3x^2 + x + 2) : (x^2 - 1)
Làm các phép tính sau :
a) \(\left(\dfrac{x^2}{y^2}+\dfrac{y}{x}\right):\left(\dfrac{x}{y^2}-\dfrac{1}{y}+\dfrac{1}{x}\right)\)
b) \(\left(\dfrac{1}{x^2+4x+4}-\dfrac{1}{x^2-4x+4}\right):\left(\dfrac{1}{x+2}-\dfrac{1}{x-2}\right)\)
Bài 1: Tính giá trị:
A= x^2+4y^2-2x+10+4xy-4y tại x+2y=5
B= (x^2+4xy+4y^2)-2(x+2y)(y-1)+y^2-2y+1 tại x+y=5
C= x^2-y^2-4x tại x+y=2
D= x^2+y^2+2xy-4x-4y-3 tại x+y=4
E= 2x^6+3x^3y^3+y^6+y^3 tại x^3+y^3=1
Bài 2: Chứng minh rằng
a) -9x^2+12x-5<0
b) 4/9x^2-4x+9/2>0
Bài 3: Tìm giá trị lớn nhất:
A= 4-2x^2
B=(1-x)(2+x)(3+x)(6+x)
C=-2x^2-y^2-2xy+4x+2y+5
D=-9x^2+24x-18
E=-x^4+2x^3-3x^2+4x-1