B1Tìm gtln của bt
A=4x-x^2+3
B=x-x^2
C=2x-2x^2-5
B2. Rút gọn bt
a,(6x+1)2+(6x-1)2-2(1+6x)(6x-1)
b,x(2x2-3)-x2(5x+1)+xx2
c,3(22+1)(24+1)(28+1)(216+1)
d,3x(x-2)-5x(1-x)-8(x2-3)
MK CẦN NGAY NÊN MONG M.N GIÚP VS
Bài 3: Rút gọn biểu thức:
a) (6x+1)2+(6x-1)2-2(1+6x)(6x-1); b) 3(22+1)(24+1)(28+1)(216+1); c) x(2x2-3)-x2(5x+1)+x2; d) 3x(x-2)-5x(1-x)-8(x2-3)
Bài 2. Tính:
a. (x – 2y)2 b. (2x2 +3)2 c. (x – 2)(x2 + 2x + 4) d. (2x – 1)3
Bài 3: Rút gọn biểu thức
1. (6x + 1)2 + (6x – 1)2 – 2(1 + 6x)(6x – 1) 2. 3(22 + 1)(24 + 1)(28 + 1)(216 + 1)
3. x(2x2 – 3) – x2(5x + 1) + x2. 4. 3x(x – 2) – 5x(1 – x) – 8(x2 – 3)
HEPL ME!
Bài 2
a. (x-2y)2 =2x-4y
b. (2x^2 +3)2 =4x^2+6
c. (x-2) (x^2+2x+4) = x^3-8 (hằng đẳng thức)
d. (2x-1)3 = 6x-3
Xin lỗi mik chỉ lm ổn bài 2 thôi!
Bài 1: Tính:
a) x2(x-2x3); b) (x2+1)(5-x); c) (x-2)(x2+3x-4); d) (x-2)(x-x2+4); e) (x2-1)(x2+2x); f) (2x-1)(3x+2)(3-x)
Bài 2: Tính:
a) (x-2y)2; b) (2x2+3)3; c) (x-2)(x2+2x+4); d) (2x-1)3
Bài 3: Rút gọn biểu thức:
a) (6x+1)2+(6x-1)2-2(1+6x)(6x-1); b) 3(22+1)(24+1)(28+1)(216+1); c) x(2x2-3)-x2(5x+1)+x2; d) 3x(x-2)-5x(1-x)-8(x2-3)
Bài 4: Tính nhanh:
a) 1012; b) 97.103; c) 772+232+77.46; d) 1052-52; e) A= (x-y)(x2+xy+y2)+2y3 tại x= \(\dfrac{2}{3}\) và y= \(\dfrac{1}{3}\)
Bạn chú ý đăng lẻ câu hỏi! 1/
a/ \(=x^3-2x^5\)
b/\(=5x^2+5-x^3-x\)
c/ \(=x^3+3x^2-4x-2x^2-6x+8=x^3=x^2-10x+8\)
d/ \(=x^2-x^3+4x-2x+2x^2-8=3x^2-x^3+2x-8\)
e/ \(=x^4-x^2+2x^3-2x\)
f/ \(=\left(6x^2+x-2\right)\left(3-x\right)=17x^2+5x-6-6x^3\)
thu gọn biểu thức
a) (6x-2)2+4(3x-1)(2+y)+(y+2)2-(6x+y)2
b)5(2x-1)2+2(x-1)(x+3)-2(5-2x)2-2x(7x+12)
c)2(5x-1)(x2-5x+1)+(x2-5x+1)2+(5x-1)2-(x2-1)(x2+1)
d)(x2+4)2-(x2+4)(x2-4)(x2+16)-8(x-4)(x+4)
`#3107`
`a)`
`(6x - 2)^2 + 4(3x - 1)(2 + y) + (y + 2)^2 - (6x + y)^2`
`= [(6x - 2)^2 - (6x + y)^2] + 4(3x - 1)(2 + y) + (2 + y)^2`
`= (6x - 2 - 6x - y)(6x -2 + 6x + y) + (2 + y)*[ 4(3x - 1) + 2 + y]`
`= (2 - y)(12x + y - 2) + (2 + y)*(12x - 4 + 2 + y)`
`= (2 - y)(12x + y - 2) + (2 + y)*(12x + y - 2)`
`= (12x + y - 2)(2 - y + 2 + y)`
`= (12x + y - 2)*4`
`= 48x + 4y - 8`
`b)`
\(5(2x-1)^2+2(x-1)(x+3)-2(5-2x)^2-2x(7x+12)\)
`= 5(4x^2 - 4x + 1) + 2(x^2 + 2x - 3) - 2(25 - 20x + 4x^2) - 14x^2 - 24x`
`= 20x^2 - 20x + 5 + 2x^2 + 4x - 6 - 50 + 40x - 8x^2 - 14x^2 - 24x`
`= - 51`
`c)`
\(2(5x-1)(x^2-5x+1)+(x^2-5x+1)^2+(5x-1)^2-(x^2-1)(x^2+1)\)
`= [ 2(5x - 1) + x^2 - 5x + 1] * (x^2 - 5x + 1) + (5x - 1)^2 - [ (x^2)^2 - 1]`
`= (10x - 2 + x^2 - 5x + 1) * (x^2 - 5x + 1) + (5x - 1)^2 - x^4 + 1`
`= (x^2 + 5x - 1)(x^2 - 5x + 1) + (5x - 1)^2 - x^4 + 1`
`= x^4 - (5x - 1)^2 + (5x - 1)^2 - x^4 + 1`
`= 1`
`d)`
\((x^2+4)^2-(x^2+4)(x^2-4)(x^2+16)-8(x-4)(x+4)\)
`= (x^2 + 4)*[x^2 + 4 - (x^2 - 4)(x^2 + 16)] - 8(x^2 - 16)`
`= (x^2 + 4)(x^4 + 12x^2 - 64) - 8x^2 + 128`
`= x^6 + 16x^4 - 16x^2 - 256 - 8x^2 + 128`
`= x^6 + 16x^4 - 24x^2 - 128`
Bài 1: Rút gọn rồi tính giá trị biểu thức:
a) A = 4x2.(-3x2 + 1) + 6x2.( 2x2 – 1) + x2 khi x = -1
b) B = x2.(-2y3 – 2y2 + 1) – 2y2.(x2y + x2) khi x = 0,5 và y = -1/2
Bài 2: Tìm x, biết:
a) 2(5x - 8) – 3(4x – 5) = 4(3x – 4) +11
b) 2x(6x – 2x2) + 3x2(x – 4) = 8
c) (2x)2(4x – 2) – (x3 – 8x2) = 15
Bài 3: Chứng tỏ rằng giá trị của biểu thức sau không phụ thuộc vào giá trị của biến x:
P = x(2x + 1) – x2(x+2) + x3 – x +3
\(1,\\ a,A=4x^2\left(-3x^2+1\right)+6x^2\left(2x^2-1\right)+x^2\\ A=-12x^4+4x^2+12x^2-6x^2+x^2=-x^2=-\left(-1\right)^2=-1\\ b,B=x^2\left(-2y^3-2y^2+1\right)-2y^2\left(x^2y+x^2\right)\\ B=-2x^2y^3-2x^2y^2+x^2-2x^2y^3-2x^2y^2\\ B=-4x^2y^3-4x^2y^2+x^2\\ B=-4\left(0,5\right)^2\left(-\dfrac{1}{2}\right)^3-4\left(0,5\right)^2\left(-\dfrac{1}{2}\right)^2+\left(0,5\right)^2\\ B=\dfrac{1}{8}-\dfrac{1}{4}+\dfrac{1}{4}=\dfrac{1}{8}\)
\(2,\\ a,\Leftrightarrow10x-16-12x+15=12x-16+11\\ \Leftrightarrow-14x=-4\\ \Leftrightarrow x=\dfrac{2}{7}\\ b,\Leftrightarrow12x^2-4x^3+3x^3-12x^2=8\\ \Leftrightarrow-x^3=8=-2^3\\ \Leftrightarrow x=2\\ c,\Leftrightarrow4x^2\left(4x-2\right)-x^3+8x^2=15\\ \Leftrightarrow16x^3-8x^2-x^3+8x^2=15\\ \Leftrightarrow15x^3=15\\ \Leftrightarrow x^3=1\Leftrightarrow x=1\)
\(P=x\left(2x+1\right)-x^2\left(x+2\right)+x^3-x+3\\ P=2x^2+x-x^3-2x^2+x^3-x+3\\ P=3\left(đfcm\right)\)
Rút gọn các biểu thức
a. x(2x2 – 3) – x2(5x + 1) + x2
b. 3x(x – 2) – 5x(1 – x) – 8(x2 – 3)
c. 1/2 x2(6x – 3) – x( x2 + 1/2 (x + 4)
a. x(2x2 – 3) – x2(5x + 1) + x2
= 2x3 – 3x – 5x3 – x2 + x2 = -3x – 3x3
b. 3x(x – 2) – 5x(1 – x) – 8(x2 – 3)
= 3x2 – 6x – 5x + 5x2 – 8x2 + 24
= - 11x + 24
c. 1/2 x2(6x – 3) – x( x2 + 1/2 (x + 4)
= 3x3 - 3/2 x2 – x3 - 1/2 x + 1/2 x + 2
= 2x3 - 3/2 x2 + 2
a, x(2x2-3)-x2(5x+1)x2
=2x3-3x-5x3- x2+x2=-3x-3x3
học tốt nhé!!
b, 3x(x-2)-5x(1-x)-8(x2-3)
=3x2-6x-5x+5x2-8x2+24
=-11x+24
Bài 1: Rút gọn các biểu thức sau:
a, A = (x-2).(2x-1) - 2x (x+3)
b, B = (3x-2).(2x+1) - (6x-1).(x+2)
c, C = 6x.(2x+3) - (4x-1).(3x-2)
d, D = (2x+3).(5x-2)+(x+4).(2x-1) - 6x.(2x-3)
Bài 2: Chứng tỏ rằng các đa thức không phụ thuộc vào biến.
a, 2x(3x-5).(x+11) - 3x.(2x+3).(x+7)
b, (x2+5x-6).(x-1) - (x+2).(x2-x+1) - x(3x-10)
c, (x2+x+1).(x-1) - x2(x+1) + x2 - 5
Bài 1
A= (x-2)(2x-1)-2x(x+3)=2x2-x-4x+2-2x2-6x=-11x+2
Bài 1:
a) \(A=\left(x-2\right)\left(2x-1\right)-2x\left(x+3\right)\)
\(A=2x^2-x-4x+2-2x^2-6x\)
\(A=-11x+2\)
b) \(B=\left(3x-2\right)\left(2x+1\right)-\left(6x-1\right)\left(x+2\right)\)
\(B=6x^2+3x-4x-2-6x^2-12x+x+2\)
\(B=-12x\)
c) \(C=6x\left(2x+3\right)-\left(4x-1\right)\left(3x-2\right)\)
\(C=12x^2+18x-12x^2+8x+3x-2\)
\(C=29x-2\)
d) \(D=\left(2x+3\right)\left(5x-2\right)+\left(x+4\right)\left(2x-1\right)-6x\left(2x-3\right)\)
\(D=10x^2-4x+15x-6+2x^2-x+8x-4-12x^2+18x\)
\(D=36x-10\)
Bài 2:
a: Ta có: \(2x\left(3x-5\right)\left(x+11\right)-3x\left(2x+3\right)\left(x+7\right)\)
\(=2x\left(3x^2+33x-5x-55\right)-3x\left(2x^2+14x+3x+21\right)\)
\(=6x^3+56x^2-110x-6x^2-51x^2-63x\)
\(=-117x\)
b: Ta có: \(\left(x^2+5x-6\right)\left(x-1\right)-\left(x+2\right)\left(x^2-x+1\right)-x\left(3x-10\right)\)
\(=x^3+4x^2-11x+6-\left(x^3-x^2+x+2x^2-2x+2\right)-3x^2+10x\)
\(=x^3+x^2-x+6-x^3-x^2+x-2\)
=4
c: Ta có: \(\left(x^2+x+1\right)\left(x-1\right)-x^2\left(x+1\right)+x^2-5\)
\(=x^3-1-x^3-x^2+x^2-5\)
=-6
Rút gọn biểu thức:
a) (6x + 1)^2 + (6x-1)^2 - 2(1+6x)(6x-1)
b) 3(2^2 +1) (2^4 +1) (2^8 +1)(2^16 +1)
c) x(2x^2 - 3) -x^2 (5x +1) +x^2
d) 3x(x-2) - 5x(1-x) - 8(x^2 - 3)
a) \(\left(6x+1\right)^2+\left(6x-1\right)^2-2\left(1+6x\right)\left(6x-1\right)\)
\(=36x^2+12x+1+36x^2-12x+1-72x^2+2\)
\(=4\)
c) \(x\left(2x^2-3\right)-x^2\left(5x+1\right)+x^2\)
\(=2x^3-3x-5x^3-x^2+x^2\)
\(=-3x^3-3x\)
d) \(3x\left(x-2\right)-5x\left(1-x\right)-8\left(x^2-3\right)\)
\(=3x^2-6x-5x+5x^2-8x^2+24\)
\(=-11x+24\)
Rút gọn phân thức
a) (6x+1)^2 + (6x-1)^2 - 2(1+6x).(6x-1)
b) x(2x^2 - 3) - x^2(5x+1) + x^2
c) 3(2^2+1).(2^4+1).(2^8+1).(2^16+1)
d) 3x(x - 2) - 5x(1 - x) - 8(x^2 - 3)
a) (6x+1)2 + (6x-1)2 - 2(1+6x)(6x-1)
= (6x+1+6x-1)2
=144x2
b) x(2x2 -3) - x2(5x+1) +x2
=2x3 - 3x - 5x3 -x2+x2
=-3x3-3x
=-3x(x2+1)
c) 3(22+1)(24+1)(28+1)(216+1)
= (22-1)(22+1)(24+1)(28+1)(216+1)
= (24-1)(24+1)(28+1)(216+1)
= (28-1)(28+1)(216+1)
= (216-1)(216+1)
= 232 -1
d) 3x(x-2) - 5x(1-x) - 8(x2 -3)
= 3x2-6x - 5x + 5x2 - 8x2 +24
= -11x +24
a) = (6x+1)2 -2(6x+1)(6x-1)+(6x-1)2=(6x+1-6x+1)2=22=4