a) ( 3 + x )2 = x2 + 6x + 9
b) ( 5 - x )3 = 125 - 75x + 45x2 - x3
c) ( 2x - 1 )( x2 - x + 3 ) = 2x3 - 2x2 + 6x - x2 + x - 3 = 2x3 - 3x2 + 7x - 3
d) \(\frac{9}{x^2+3x}-\frac{3-x}{x}=\frac{9}{x\left(x+3\right)}+\frac{x-3}{x}\)
\(=\frac{9}{x\left(x+3\right)}+\frac{\left(x-3\right)\left(x+3\right)}{x\left(x+3\right)}\)
\(=\frac{9+x^2-9}{x\left(x+3\right)}=\frac{x^2}{x\left(x+3\right)}=\frac{x}{x+3}\)
a, \(\left(3+x\right)^2=9+6x+x^2\)
b, \(\left(5-x\right)^3=125-75x+15x^2-x^3\)
c, \(\left(2x-1\right)\left(x^2-x+3\right)=2x^3-2x^2+6x-x^2+x-3=2x^3-3x^2+7x-3\)
d, \(\frac{9}{x^2+3x}-\frac{3-x}{x}=\frac{9}{x\left(x+3\right)}-\frac{3-x}{x}=\frac{9}{x\left(x+3\right)}+\frac{\left(x-3\right)\left(x+3\right)}{x\left(x+3\right)}\)
\(=\frac{9+x^2-9}{x\left(x+3\right)}=\frac{x^2}{x\left(x+3\right)}\)
a, \(\left(3+x\right)^2=9+6x+x^2=x^2+6x+9\)
b, \(\left(5-x\right)^3=125-75x+15x^2-x^3=x^3+15x^2-75x+125\)
c, \(\left(2x-1\right)\left(x^2-x+3\right)=2x^3-2x^2+6x-x^2+x-3=2x^3-3x^2+7x-3\)
d, \(\frac{9}{x^2+3x}-\frac{3-x}{x}=\frac{9}{x\left(x+3\right)}-\frac{3-x}{x}=\frac{9}{x\left(x+3\right)}+\frac{\left(x-3\right)\left(x+3\right)}{x\left(x+3\right)}\)
\(=\frac{9+x^2-9}{x\left(x+3\right)}=\frac{x^2}{x\left(x+3\right)}\)
Bổ sung nhé, thường thường thì mình cũng hay quên rút gọn x bỏ qua cho mình nhé !
\(\frac{x^2}{x\left(x+3\right)}=\frac{x}{x+3}\)