Question

tìm x:

17–14(x+1)=13–4(x+1)–5(x-3)

7(4x+3)-4(x-1)=15(X+0,75)+7

3x(x+1)−2x(x+2)=x mũ 2 – 1

Bạn nào giúp mik VS ;)

 

Answer 1

a) 17 - 14( x + 1 ) = 13 - 4( x + 1 ) - 5( x - 3 )

<=> 17 - 14x - 14 = 13 - 4x - 4 - 5x + 15

<=> 17 - 14 - 13 + 4 - 15 = -4x - 5x + 14x 

<=> -21 = 5x

<=> x = -21/5

b) 7( 4x + 3 ) - 4( x - 1 ) = 15( x + 0, 75 ) + 7

<=> 28x + 21 - 4x + 4 = 15x + 45/4 + 7

<=> 28x - 4x - 15x = 45/4 + 7 - 21 - 4

<=> 9x = -27/4

<=> x = -3/4

c) 3x( x + 1 ) - 2x( x + 2 ) = x² - 1

<=> 3x² + 3x - 2x² - 4x = x² - 1

<=> 3x² + 3x - 2x² - 4x - x² = -1

<=> -x = -1

<=> x = 1 

Answer 2

a, \(17-14\left(x+1\right)=13-4\left(x+1\right)-5\left(x-3\right)\)

\(\Leftrightarrow17-14x-14=13-4x-4-5x+15\)

\(\Leftrightarrow3-14x=24-9x\Leftrightarrow3-14x-24+9x=0\)

\(\Leftrightarrow-21-5x=0\Leftrightarrow5x=-21\Leftrightarrow x=-\frac{21}{5}\)

b, \(7\left(4x+3\right)-4\left(x-1\right)=15\left(x+0,75\right)+7\)

\(\Leftrightarrow28x+21-4x+1=15x+\frac{45}{4}+7\)

\(\Leftrightarrow9x=-\frac{27}{4}\Leftrightarrow x=-\frac{3}{4}\)

c, \(3x\left(x+1\right)-2x\left(x+2\right)=x^2-1\)

\(\Leftrightarrow3x^2+3x-2x^2-4x=x^2-1\)

\(\Leftrightarrow x^2-x=x^2-1\Leftrightarrow x=1\)