Question

Cho f(x)=(x-4)-3(x+1). Tìm x sao cho f(x)=4.

Answer 1

\(f\left(x\right)=\left(x-4\right)-3\left(x+1\right)\)

\(f\left(x\right)=4\Leftrightarrow\left(x-4\right)-3\left(x+1\right)=4\)

\(\Leftrightarrow x-4-3x-3-4=0\)

\(\Leftrightarrow-2x-11=0\)

\(\Leftrightarrow-2x=11\)

\(\Leftrightarrow x=-\frac{11}{2}\)

Answer 2

Bài làm:

\(f\left(x\right)=4\)

\(\Leftrightarrow\left(x-4\right)-3\left(x+1\right)=4\)

\(\Leftrightarrow x-4-3x-3=4\)

\(\Leftrightarrow-2x=11\)

\(\Leftrightarrow x=-\frac{11}{2}\)