Question

-2x+3.{12-2[3x-(20+2x)-4x]+1}=45

Answer 1

Ta có :-2x + 3x . { 12-2.[ 3.x-(20+2.x) - 4.x ] + 1 } = 45

<=>-2.x +3.x. [ 12-2 .( 3.x - 20 - 2.x  - 4.x )+1 ) = 45

<=> -2.x + 3.x . [ 12- 2 ( -3.x -20 ) + 1 ] = 45

<=> -2.x + 3.x . ( 12 + 6.x + 40 + 1 )  = 45

<=>-2.x + 3.x . ( 53 + 6.x ) = 45

<=> -2.x + 159.x + 18.x² = 45

<=> 157 .x + 18.x² = 45

<=> 157.x + 18.x² - 45 = 0

<=> 18.x² - 5.x + 162.x - 45 = 0

<=> x. ( 18.x-5 ) + 9 .( 18.x-5) = 0

<=> ( 18.x-5 ) . ( x + 9 ) = 0

<=> \(\orbr{\begin{cases}18.x-5=0\\x+9=0\end{cases}}\)

<=> \(\orbr{\begin{cases}x=\frac{5}{18}\\x=-9\end{cases}}\)

Vậy x = { \(\frac{5}{18};-9\)}