m(x) = 3h(x) - 2f(x) = 3( 2$x^{3}$ + 4x + 1) - 2( 5$x^{3}$ - 7x² + x + 7 )
m(x) = 2.3$x^{3}$ + 3.4x + 3.1 - 2.5$x^{3}$ + 2.7x² - 2x - 2.7
m(x) = 6$x^{3}$ + 12x + 3 - 10$x^{3}$ + 14x² - 2x - 14
m(x) = ( 6$x^{3}$ - 10$x^{3}$ ) + 14x² + ( 12x - 2x ) + ( 3 - 14 )
m(x) = - 4$x^{3}$ + 14x² + 10x - 11
Xin hay nhất ạ :)