Rút gọn biểu thức sau: \(\sqrt{x^4}\)+ 2x2 + 1
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(5x3 – 4x2) : 2x2 + (3x4 + 6x) : 3x – x(x2 – 1)
= 5x3 : 2x2 + (-4x2): 2x2 + 3x4 : 3x + 6x : 3x – [x. x2 + x . (-1)]
= (5:2) . (x3 : x2) + [(-4) : 2] . (x2 : x2) + (3 : 3) . (x4 : x) + (6 : 3). (x:x) – ( x3 – x)
= \(\dfrac{5}{2}\)x – 2 + x3 + 2 – x3 + x
= (x3 – x3) + (\(\dfrac{5}{2}\)x + x) + (-2 + 2)
= 0 + \(\dfrac{7}{2}\)x + 0
= \(\dfrac{7}{2}\)x
A = − 6 x 5 + 4 x 4 + 2 x 3 − 2 x 2 + 2 x 3 − 6 x 2 + 2 x
A = − 6 x 5 + 4 x 4 + 4 x 3 − 8 x 2 + 2 x
Chọn đáp án C
ĐKXĐ: \(x\ne\pm2\)
\(\dfrac{2x^2-x^3}{x^2-4}=\dfrac{x^2\left(2-x\right)}{\left(x-2\right)\left(x+2\right)}=\dfrac{-x^2\left(x-2\right)}{\left(x-2\right)\left(x+2\right)}\)
\(=\dfrac{-x^2}{x+2}\)
\(---\)
ĐKXĐ: \(x\ne-1\)
\(\dfrac{x+1}{x^3+1}=\dfrac{x+1}{\left(x+1\right)\left(x^2-x+1\right)}=\dfrac{1}{x^2-x+1}\)
\(A=\dfrac{x+12}{x-4}+\dfrac{1}{\sqrt{x}+2}-\dfrac{4}{\sqrt{x}-2}\)
\(=\dfrac{x+12+\sqrt{x}-2-4\left(\sqrt{x}+2\right)}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\)
\(=\dfrac{x+\sqrt{x}+10-4\sqrt{x}-8}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\)
\(=\dfrac{x-3\sqrt{x}+2}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\)
\(=\dfrac{\left(\sqrt{x}-2\right)\left(\sqrt{x}-1\right)}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}=\dfrac{\sqrt{x}-1}{\sqrt{x}+2}\)
a.\(A=\dfrac{x^2-4x+4}{x^3-2x^2-\left(4x-8\right)}=\dfrac{\left(x-2\right)^2}{x^2\left(x-2\right)-4\left(x-2\right)}=\dfrac{\left(x-2\right)^2}{\left(x^2-4\right)\left(x-2\right)}=\dfrac{x-2}{\left(x-2\right)\left(x+2\right)}=\dfrac{1}{x+2}\)
\(A=\dfrac{\left(x-2\right)^2}{x^2\left(x-2\right)-4\left(x-2\right)}\left(x\ne\pm2\right)\\ A=\dfrac{\left(x-2\right)^2}{\left(x-2\right)^2\left(x+2\right)}=\dfrac{1}{x+2}\\ B=\dfrac{x+2-x+\sqrt{x}-1}{\left(\sqrt{x}+1\right)\left(x-\sqrt{x}+1\right)}\cdot\dfrac{4\sqrt{x}}{3}\left(x>0\right)\\ B=\dfrac{4\sqrt{x}\left(\sqrt{x}+1\right)}{3\left(\sqrt{x}+1\right)\left(x-\sqrt{x}+1\right)}=\dfrac{4\sqrt{x}}{3\left(x-\sqrt{x}+1\right)}\)
a) Ta có: 2x2 + 8 = 2(x2 + 4).
8 – 4x + 2x2 – x3
= (8 – x3) - ( 4x - 2x2)
= (2 – x).(4 + 2x + x2) - 2x.(2 - x)
= (2 – x).(4 + 2x + x2 – 2x)
= (2 - x). (4 + x2 )
* Do đó:
b) Tại x = 1 2 hàm số đã cho xác định nên thay x = 1 2 vào biểu thức rút gọn của P ta được:
\(3x^2+1\)