Question

-3x(2x+1)+5(-x+2)=5x-9

15-2(x-3)=x

[2(x-2)-2]-2=2

Answer 1

Salut,

-3x(2x+1)+5(-x+2)=5x-9

-6x²-3x-5x+10=5x-9

-6x²-8x+10-5x+9=0

-6x²-13x+19=0

Δ=(-13)²-4*(-6)*19=625>0

x1=(13+√625)/2=(13+25)/2=38/2=19;

x2=(13-√625)/2=(13-25)/2=-12/2=-6.

15-2(x-3)=x

15-2x+6=x

21-2x=x

x+2x=21

3x=21

x=21/3

x=7.

[2(x-2)-2]-2=2

[2x-4-2]-2=2

[2x-6]-2=2

2x-6-2=2

2x-8=2

2x=2+8

2x=10

x=10/2

x=5.

Bafta!

Answer 2

- 3 ( 2 x + 1 ) + 5 ( - x + 2 ) = 5 x - 9

- 6 x - 3 - 5 x + 10 - 5 x = - 9

- 11 x - 5 x = - 9 - 7

- 16 x = - 16

x = ( - 16 ) : ( - 16 )

x = 1

Daca x inaintea parantezei este litera atunci solutia este:

-3 x ( 2 x + 1 ) + 5( - x + 2 )= 5 x - 9

- 6 x² - 3 x - 5 x + 10 - 5 x + 9 = 0

- 6 x² - 13 x + 19 = 0 l : ( - )

6 x² + 13 x - 19 = 0

Δ = 169 + 4 × 6 × 19 = 169 + 456 = 625

x₁ = ( - 13 + √625 ) / 12 = ( - 13 + 25 ) / 12 = 12 / 12 = 1

x₂ = ( - 13 - 25 ) / 12 = - 38 / 12 = - 19 / 6

15 - 2 ( x - 3 ) = x

15 - 2 x + 6 = x

- 2 x - x = - 21

- 3 x = - 21

x = ( - 21) : ( - 3 )

x = 7

[ 2 ( x - 2 ) - 2 ] - 2 = 2

( 2 x - 4 - 2 ) - 2 = 2

2 x - 6 = 2 + 2

2 x = 4 + 6

2 x = 10

x = 10 : 2

x = 5