Question

x(5-2x)+(x-1)=15

Answer 1

\(x\left(5-2x\right)+\left(x-1\right)=15\Rightarrow5x-10x+x-1=15\)

\(\Rightarrow-4x-1=15\Rightarrow-4x=16\Rightarrow x=-4\)

Vậy x=-4

Answer 2

x(5 - 2x) + (x - 1) = 15

=> 5x - 2x² + x - 1 =15

=> 2x² - 5x - x + 1 = -16

=> 2x² - 6x + 1 = -16

=> \(2\left(x-\dfrac{3}{2}\right)^2-\dfrac{9}{2}+1=-16\)

=> \(2\left(x-\dfrac{3}{2}\right)^2-\dfrac{7}{2}=-16\)

=> \(2\left(x-\dfrac{3}{2}\right)^2=-12,5\)

Vậy x \(\in\)\(\varnothing\)