Question

tìm x biết

a) x ( 5 - 2x ) + 2x ( x - 1 ) =13

b ) 9x ( x - 1 ) - (3x - 1 ) ^ 2 =11

Answer 1

a) \(x.\left(5-2x\right)+2x.\left(x-1\right)=13\)

\(\Rightarrow5x-2x^2+2x^2-2x=13\)

\(\Rightarrow3x=13\)

\(\Rightarrow x=\dfrac{13}{3}\)

b) \(9x.\left(x-1\right)-\left(3x-1\right)^2=11\)

\(\Rightarrow9x^2-9x-\left(9x^2-6x+1\right)=11\)

\(\Rightarrow3x=12\)

\(\Rightarrow x=4\)

Answer 2

a) x ( 5 - 2x) + 2x (x - 1 ) = 13

\(\Rightarrow\) 5x - 2x² + 2x³ - 2x = 13

( 5x - 2x ) + (-2x² + 2x³) = 13

3x + x =13

4x = 13

x = \(\dfrac{13}{4}\)

b) 9x ( x - 1 ) - ( 3x - 1 )² = 11

\(\Rightarrow\) 9x² - 9x - ( 9x² - 6x + 1 ) = 11

3x = 12

x = 12/3 = 4