Question

4x²-3(2x-5)-25=0

Answer 1

\(4x^2-3\left(2x-5\right)-25=0\Leftrightarrow4x^2-6x-10=0\)

\(\Leftrightarrow2\left(2x^2-3x-5\right)=0\Leftrightarrow2\left(x+1\right)\left(2x-5\right)=0\Leftrightarrow x=-1;x=\dfrac{5}{2}\)

Answer 2

4x²-3(2x-5)-25=0

⇒(2x)²-5²-3(2x-5)=0

⇒(2x-5)(2x+5)-3(2x-5)=0

⇒(2x-5)(2x+2)=0

⇒hoặc 2x-5=0⇒x=2,5

hoặc 2x+2=0⇒x=-1

vậy x={2,5;-1}