Cho A(x) = 3x^4 - 3/4x^3 + 2x^2 - 3; B(x) = 8x^4 + 1/5x^3 - 9x + 2/5.Tính A(x) + B(x).
Giải thích
\(A\left( x \right) + B(x) = 3{x^4} - \frac{3}{4}{x^3} + 2{x^2} - 3 + 8{x^4} + \frac{1}{5}{x^3} - 9x + \frac{2}{5}\)
\( = (3{x^4} + 8{x^4}) + \left( { - \frac{3}{4}{x^3} + \frac{1}{5}{x^3}} \right) + 2{x^2} - 9x + \left( { - 3 + \frac{2}{5}} \right)\)
\( = 11{x^4} - \frac{{11}}{{20}}{x^3} + 2{x^2} - 9x - \frac{{13}}{5}\)