Question

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

Answer 1

\(Ta\) \(có\): \(f\left(x\right)=4\)

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

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

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

\(\Rightarrow-2x-7=4\)

\(\Rightarrow-2x=11\)

\(\Rightarrow x=-\dfrac{11}{2}\)

Answer 2

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

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

\(\rightarrow-2x=11\rightarrow x=-\dfrac{11}{2}\)