Question

câu 6: (x-5)(x-4)=10-2x

câu 7:(x ²+1)(x-2)+2x=4

câu 8:(x+3)(x ²-3x+9)=7x ³+21x

Answer 1

Câu 7: 

\(\Leftrightarrow\left(x-2\right)\left(x-1\right)\left(x+1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=1\\x=-1\end{matrix}\right.\)

Answer 2

6, (x-5).(x-4)=10-2x

(x-5).(x-4)+2(x-5)=0

(x-5)(x-2)=0

=>x=5, x=2

7, (x^2+1)(x-2)+2x=4

x^3-2x^2+x-2+2x=4

x^3-2x^2+3x-2-4=0

x^3-2x^2+3x-6=0

x^2(x-2)+3(x-2)=0

(x-2)(x^2+3)=0

th1: x=2

th2: x^2+3>0 với mọi x thuộc Z

8, ( đề cs sai hông , giải hong ra:>)