Thực hiện phép tính
a. (1/2 x – 1)(2x – 3)
b. (x – 7)(x – 5)
c. (x - 1/2 )(x + 1/2 )(4x - 1)
Mn giúp mk vs ạ, mk cảm ơn
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\(\left(\frac{a}{b^2}+\frac{1}{a}-\frac{1}{b}\right):\left(\frac{b}{a}+\frac{a^2}{b^2}\right)=\left(\frac{a^2+b^2-ab}{ab^2}\right):\left(\frac{b^3+a^3}{ab^2}\right)=\frac{a^2+b^2-ab}{\left(a^3+b^3\right)}\)
\(=\frac{a^2+b^2-ab}{\left(a+b\right)\left(a^2+b^2-ab\right)}=\frac{1}{a+b}\)
\(\left(x^3+x^2y+xy^2+y^3\right)\left(x-y\right)=x^4-x^3y+x^3y-x^2y^2+x^2y^2-xy^3+xy^3-y^4=x^4-y^4\)
3x3 - 5x2 + 5x - 2
= 3x3 - 2x2 - 3x2 +2x + 3x-2
= x2(3x -2) - x(3x -2) + (3x-2)
= (3x-2)(x2 -x +1)
ta có : \(\hept{\begin{cases}\left(a+b\right)\left(a^2-b^2\right)=a^3-b^3-ab^2+a^2b\\\left(b+c\right)\left(b^2-c^2\right)=b^3-c^3-bc^2+b^2c\\\left(a+c\right)\left(c^2-a^2\right)=c^3-a^3-ca^2+c^2a\end{cases}}\)
Vậy biểu thức bằng : \(a^2b-ab^2+b^2c-bc^2+c^2a-ca^2=ab\left(a-b\right)+bc\left(b-c\right)+ca\left(c-a\right)\)
\(=ab\left(a-b\right)+bc\left(b-c\right)-ca\left(a-b\right)-ca\left(b-c\right)=a\left(b-c\right)\left(a-b\right)+c\left(b-a\right)\left(b-c\right)\)
\(=\left(a-b\right)\left(b-c\right)\left(a-c\right)\)
a. (\(\frac{1}{2}\) x – 1) (2x – 3)
= x2 - \(\frac{3}{2}\) x – 2x + 3
= x2 - \(\frac{7}{2}\) x + 3
b. (x –7)(x –5)
= x2 – 5x – 7x + 35
= \(x^2\) – 12x + 35
c. (x - \(\frac{1}{2}\) )(x + \(\frac{1}{2}\) )(4x - 1)
= (\(x^2\) + \(\frac{1}{2}\) x - \(\frac{1}{2}\) x - \(\frac{1}{4}\) )(4x - 1)
= (\(x^2\) - \(\frac{1}{4}\) )(4x - 1)
= 4\(x^3\) – \(x^2\) – x + \(\frac{1}{4}\)
a, \(\left(\frac{1}{2}x-1\right)\left(2x-3\right)=x^2-\frac{3}{2}x-2x+3=x^2-\frac{7}{2}x+3\)
b, \(\left(x-7\right)\left(x-5\right)=x^2-12x+35\)
c, \(\left(x-\frac{1}{2}\right)\left(x+\frac{1}{2}\right)\left(4x-1\right)=\left(x^2-\frac{1}{4}\right)\left(4x-1\right)=4x^3-x^2-x+\frac{1}{4}\)