Question

Cho đa thức F(x) = ax + b. Xác định a, b biết F(1) = 3, F(-2) = 2

Answer 1

Ta có :

\(f\left(x\right)=ax+b\)

+) \(f\left(1\right)=3\)

\(\Leftrightarrow a.1+b=3\)

\(\Leftrightarrow a+b=3\)\(\left(1\right)\)

+) \(f\left(-2\right)=2\)

\(\Leftrightarrow a.\left(-2\right)+b=2\)

\(\Leftrightarrow-2a+b=2\left(2\right)\)

Từ \(\left(1\right)+\left(2\right)\Leftrightarrow\left(a-b\right)+\left(-2a+b\right)=3+2\)

\(\Leftrightarrow-1a=5\)

\(\Leftrightarrow a=5\)

\(\Leftrightarrow b=-2\)

Vậy ....