Lời giải:
a, \(F\left(x\right)=-3x+6\)
\(F\left(x\right)=-3x+6=0\)
\(\Rightarrow x=2\)
Vậy, .....
b, \(G\left(x\right)=5x-10\)
\(G\left(x\right)=5x-10=0\)
\(\Rightarrow x=2\)
Vậy, ....
d, \(M\left(x\right)=x^2+7x-8\)
\(M\left(x\right)=x^2+7x-8=0\)
\(\Rightarrow\left(x^2+8x\right)-\left(x+8\right)=0\)
\(\Rightarrow x\left(x+8\right)-\left(x+8\right)=0\)
\(\Rightarrow\left(x+8\right)\left(x-1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x+8=0\\x-1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-8\\x=1\end{matrix}\right.\)
Vậy, ....
e, \(L\left(x\right)=5x^2+9x+4\)
\(L\left(x\right)=5x^2+9x+4=0\)
\(\Rightarrow\left(5x^2+5x\right)+\left(4x+4\right)=0\)
\(\Rightarrow5x\left(x+1\right)+4\left(x+1\right)=0\)
\(\Rightarrow\left(x+1\right)\left(4+5x\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x+1=0\\4+5x=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=-1\\\dfrac{-4}{5}\end{matrix}\right.\)
Vậy, ....
F(x)=-3x+6=0
<=>-3(x-2)=0
<=>x-2=0
<=>x=2
Vậy...
G(x)=5x-10=0
<=>5(x-2)=0
<=>x-2=0
<=>x=2
Vậy...
K(sai đề)
M(x)=x2+7x-8=0
<=>(x2+8x)-(x+8)=0
<=>x(x+8)-(x+8)=0
<=>(x+8)(x-1)=0
<=>x+8=0 hoặc x-1=0
<=>x=-8 hoặc x=1
Vậy...
L(x)=5x2+9x+4=0
<=>(5x2+5x)+(4x+4)=0
<=>5x(x+1)+4(x+1)=0
<=>(x+1)(5x+4)=0
<=>x+1=0 hoặc 5x+4=0
<=>x=-1 hoặc x=\(-\dfrac{4}{5}\)
Vậy...
