Question

tim x

a,(x-3)^3-(x-3)(x^2+3x+9)+9(x+1)^2=4

b,x(x-5)(x+5)-(x+2)(x^2-2x+4)=17

 

Answer 1

a) \(pt< =>x^3-3.x^2.3+3.x.9-27-\left(x^3-27\right)+9\left(x^2+2x+1\right)=4\)

\(< =>x^3-27-x^3+27-9x^2+27x+9x^2+18x+9=4\)

\(< =>45x=4-9=-5< =>x=-\frac{5}{45}=-\frac{1}{9}\)

b) \(pt< =>x\left(x^2-25\right)-\left(x^3+8\right)=17\)

\(< =>x^3-25x-x^3-8=17< =>25x=-8-17=-25< =>x=-1\)

Answer 2

a) ( x - 3 )³ - ( x - 3 )( x² + 3x + 9 ) + 9( x + 1 )² = 4

<=> x³ - 9x² + 27x - 27 - ( x³ - 27 ) + 9( x² + 2x + 1 ) = 4

<=> x³ - 9x² + 27x - 27 - x³ + 27 + 9x² + 18x + 9 = 4

<=> 45x + 9 = 4

<=> 45x = -5

<=> x = -5/45 = -1/9

b) x( x - 5 )( x + 5 ) - ( x + 2 )( x² - 2x + 4 ) = 17

<=> x( x² - 25 ) - ( x³ + 2³ ) = 17

<=> x³ - 25x - x³ - 8 = 17

<=> -25x - 8 = 17

<=> -25x = 25

<=> x = -1