Tính :
(a -x) / (6x^2 - ax - 2a^2) + (a+x) / (3x^2 + 4x - 4a^2)
bài này mk chưa giải được . mong mn giúp mk . cảm ơn nhiều !
K
Khách
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14 tháng 7 2019
Mình ko ghi lại đề , bạn ghi ra xong rồi suy ra như mình nha .
1) \(=>A=\left(6x^2+3x-10x-5\right)-\left(6x^2+14x-9x-21\right)\)
\(=>A=-12x+16\)
2) \(=>B=8x^3+27-8x^3+2=29\)
3)\(=>C=[\left(x-1\right)-\left(x+1\right)]^3=\left(-2\right)^3=-8\)
4)\(=>D=[\left(2x+5\right)-\left(2x\right)]^3=5^3=125\)
5)\(=>E=\left(3x+1\right)^2-\left(3x+5\right)^2+12x+2\left(6x+3\right)\)
\(=>E=\left(3x+1+3x+5\right)\left(3x+1-3x-5\right)+12x+12x+6\)
\(=>E=\left(6x+6\right)\left(-4\right)+24x+6=-24x-24+24x+6=-18\)
6)\(=>F=\left(2x^2+3x-10x-15\right)-\left(2x^2-6x\right)+x+7=-8\)
k cho mik nha ,
25 tháng 8 2017
a) x3 + 127127 = x3 + (1313)3 = (x + 1313)(x2 – x . 1313+ (1313)2)
=(x + 1313)(x2 – 1313x + 1919)
b) (a + b)3 – (a - b)3
= [(a + b) – (a – b)][(a + b)2 + (a + b) . (a – b) + (a – b)2]
= (a + b – a + b)(a2 + 2ab + b2 + a2 – b2 + a2 – 2ab + b2)
= 2b . (3a3 + b2)
c) (a + b)3 + (a – b)3 = [(a + b) + (a – b)][(a + b)2 – (a + b)(a – b) + (a – b)2]
= (a + b + a – b)(a2 + 2ab + b2 – a2 +b2 + a2 – 2ab + b2]
= 2a . (a2 + 3b2)
d) 8x3 + 12x2y + 6xy2 + y3 = (2x)3 + 3 . (2x)2 . y +3 . 2x . y + y3 = (2x + y)3
e) - x3 + 9x2 – 27x + 27 = 27 – 27x + 9x2 – x3 = 33 – 3 . 32 . x + 3 . 3 . x2 – x3 = (3 – x)3
26 tháng 10 2016
câu 1:
a,x2+2x-4z2+1
=x2+2x.1+12-(2z)2
=(x+1)2-(2z)2
=(x+1-2z)(x+1+2z)
YN
5 tháng 4 2022
`Answer:`
1) \(x\left(x+1\right)\left(x+2\right)\left(x+3\right)+1\)
\(=[x\left(x+3\right)][\left(x+1\right)\left(x+2\right)]+1\)
\(=\left(x^2+3x\right)\left(x^2+3x+2\right)+1\)
\(=\left(x^2+3x\right)^2+2.\left(x^2+3x\right)+1\)
\(=\left(x^2+3x+1\right)^2\)
2) \(\left(4x+1\right)\left(12x-1\right)\left(3x+2\right)\left(x+1\right)-4\)
\(=[\left(4x+1\right)\left(3x+2\right)][\left(12x-1\right)\left(x+1\right)]-4\)
\(=\left(12x^2+8x+3x+2\right)\left(12x^2+12x-x-1\right)-4\)
\(=[\left(12x^2+11x+0,5\right)+1,5][\left(12x^2+11x+0,5\right)-1,5]-4\)
\(=\left(12x^2+11x+0,5\right)^2-\left(1,5\right)^2-4\)
\(=\left(12x^2+11x+0,5\right)^2-\left(2,5\right)^2\)
\(=\left(12x^2+11x+0,5-2,5\right)\left(12x^2+11x+0,5+2,5\right)\)
\(=\left(12x^2+11x-2\right)\left(12x^2+11x+3\right)\)
3) \(\left(x^2+6x+5\right)\left(x^2+10x+21\right)+15\)
\(=\left(x^2+x+5x+5\right)\left(x^2+3x+7x+21\right)+15\)
\(=\left(x+1\right)\left(x+5\right)\left(x+3\right)\left(x+7\right)+15\)
\(=[\left(x+1\right)\left(x+7\right)][\left(x+5\right)\left(x+3\right)]+15\)
\(=\left(x^2+x+7x+7\right)\left(x^2+3x+5x+15\right)+15\)
\(=\left(x^2+8x+7\right)\left(x^2+8x+15\right)+15\)
Đặt \(v=x^2+=8x+11\)
Đa thức có dạng sau: \(\left(v-4\right)\left(v+4\right)+15\)
\(=v^2-4^2+15\)
\(=v^2-1\)
\(=\left(v+1\right)\left(v-1\right)\)
\(=\left(x^2+8x+11+1\right)\left(x^2+8x+11-1\right)\)
\(=\left(x^2+8x+12\right)\left(x^2+8x+10\right)\)
4) \(\left(x^2-a\right)^2-6x^2+4x+2a\)
\(=\left(x^2-a\right)\left(x^2-a\right)-6x^2+4x+2a\)
\(=\left(x^2-a\right).x^2-a\left(x^2-a\right)-6x^2+4x+2a\)
\(=x^4-ax^2-a.\left(x^2-a\right)-6x^2+4x+2a\)
\(=x^4-ax^2-\left(ax^2-aa\right)-6x^2+4x+2a\)
\(=x^4-2ax^2+a^2-6x^2+2a+4x\)
6) \(a^2-b^2-c^2+2bc-2a+1\)
\(=\left(a^2-2a+1\right)-\left(b^2-2bc+c^2\right)\)
\(=\left(a-1\right)^2-\left(b-c\right)^2\)
\(=\left(a-b+c-1\right)\left(a+b-c-1\right)\)
7) \(4a^2-4b^2+16bc-16c^2\)
\(=4a^2-\left(4b^2-16bc+16c^2\right)\)
\(=\left(2a\right)^2-\left(2b-4c\right)^2\)
\(=\left(2a-2b+4c\right)\left(2a+2b-4c\right)\)
\(=2.\left(a-b-2c\right).2\left(a+b-2c\right)\)
\(=4\left(a-b-2c\right)\left(a+b-2c\right)\)
1 tháng 10 2017
\(2x^2+2y^2-4xy+2x-2y+4\)
\(=2\left(x-y\right)^2+2\left(x-y\right)+4\)
\(=2\left[\left(x-y\right)^2+2\left(x-y\right)\frac{1}{2}+\frac{1}{4}\right]+\frac{7}{2}\)
\(=2\left(x-y+\frac{1}{2}\right)^2+\frac{7}{2}\)
\(\Rightarrow A\ge\frac{7}{2}\)
Dấu = bn tự tính nhé