Question

Tìm nghiệm của các đa thức sau:

a)M(x)=2x-\(\dfrac{1}{2}\) b)N(x)=(4x\(^2\)-1) c)P(x)=9x\(^3\)-25x

Answer 1

a, M(x)=0<=>2x-\(\dfrac{1}{2}\)=0<=>2x=\(\dfrac{1}{2}\)<=>x=\(\dfrac{1}{4}\)

vậy...

b,N(x)=0<=>4x\(^2\)-1=0<=>4x\(^2\)=1<=>x\(^2\)=\(\dfrac{1}{4}\)=\((\pm\dfrac{1}{2})^2\)

=>x=\(\pm\dfrac{1}{2}\)

vậy ...

c,P(x)=0<=>9x\(^3\)-25x=0<=>x(9x\(^2\)-25)=0

<=>\(\left\{{}\begin{matrix}x=0\\9x^2-25=0\end{matrix}\right.\)<=>\(\left\{{}\begin{matrix}x=0\\x=\pm\dfrac{3}{5}\end{matrix}\right.\)

vậy ...

Answer 2

a)M(x)=2x-\(\dfrac{1}{2}\)

2x=\(\dfrac{1}{2}\)=0

2x=0+\(\dfrac{1}{2}\)

x=\(\dfrac{1}{2}\):2

x=\(\dfrac{1}{4}\)

vậy x=\(\dfrac{1}{4}\)là nghiệm của đa thức M(x)