Đặt \(f(x) = {x^2} - 1\)
a. Ta có: \(\Delta y = f\left( {{x_0} + \Delta x} \right) - f\left( {{x_0}} \right)\)
\(= f\left( 2 \right) - f\left( 1 \right) = 3 - 0 = 3\)
b. \(\Delta y = f\left( {{x_0} + \Delta x} \right) - f\left( {{x_0}} \right)\)
\(= f\left( {0,9} \right) - f\left( 1 \right) = {\left( {0,9} \right)^2} - 1 = - 0,19\)
