Question

[phamthiminhtrang]

Tìm x :

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

Answer 1

[Huy Hoàng]

\(\left(1-3x\right)^2-\left(x-2\right)\left(9x+1\right)=\left(3x-4\right)\left(3x+4\right)-9\left(x+3\right)^2\)

<=> \(1-6x+9x^2-\left(9x^2-17x-2\right)=\left(9x^2-4\right)-\left[3\left(x+3\right)\right]^2\)

<=> \(1-6x+9x^2-9x^2+17x+2=9x^2-4-\left(3x+9\right)^2\)

<=> \(3+11x=\left(3x-3x-9\right)\left(3x+3x+9\right)-4\)

<=> \(3+4+11x=-9\left(6x+9\right)\)

<=> \(7+11x=-9.3\left(2x+3\right)\)

<=> \(7+11x=-27\left(2x+3\right)\)

<=> \(7+11x+27\left(2x+3\right)=0\)

<=> \(7+11x+54x+81=0\)

<=> \(65x=-88\)

<=> \(x=-\frac{88}{65}\)