Question

Tìm x a) 4x^2 + 20x = -25 b) x^2.(x-6) + 12x = 8

Answer 1

\(a,\Rightarrow4x^2+20x+25=0\Rightarrow\left(2x+5\right)^2=0\Rightarrow2x+5=0\Rightarrow x=-\dfrac{5}{2}\\ b,\Rightarrow x^3-6x^2+12x-8=0\Rightarrow\left(x-2\right)^3=0\Rightarrow x-2=0\Rightarrow x=2\)

Answer 2

a) \(\Rightarrow4x^2+20x+25=0\)

\(\Rightarrow\left(2x+5\right)^2=0\Rightarrow2x+5=0\)

\(\Rightarrow x=-\dfrac{5}{2}\)

b) \(\Rightarrow x^3-6x^2+12x-8=0\)

\(\Rightarrow\left(x-2\right)^3=0\Rightarrow x=2\)