Q(x)=2$x^{3}$ +x-12-$\frac{2}{7}$ x
=2$x^{3}$+(x-$\frac{2}{7}$ x)-12
=2$x^{3}$+$\frac{5}{7}$ x-12
a)P(x)+Q(x)=(2$x^{3}$+5$x^{2}$-$\frac{5}{7}$ x-4)+(2$x^{3}$+$\frac{5}{7}$ x-12)
=2$x^{3}$+5$x^{2}$-$\frac{5}{7}$ x-4+2$x^{3}$+$\frac{5}{7}$ x-12
=(2$x^{3}$+2$x^{3}$)+5$x^{2}$+(-$\frac{5}{7}$ x+$\frac{5}{7}$ x)+(-4-12)
=4$x^{3}$ +5$x^{2}$-16
b)P(x)-Q(x)=(2$x^{3}$+5$x^{2}$-$\frac{5}{7}$ x-4)-(2$x^{3}$+$\frac{5}{7}$ x-12)
=2$x^{3}$+5$x^{2}$-$\frac{5}{7}$ x-4-2$x^{3}$-$\frac{5}{7}$ x+12
=(2$x^{3}$-2$x^{3}$)+5$x^{2}$+(-$\frac{5}{7}$ x-$\frac{5}{7}$ x)+(-4+12)
=5$x^{2}$-$\frac{10}{7}$ x+8
Nếu có sai xót mong bạn góp ý.
Nhớ vote 5*, cho 1 cảm ơn, 1 câu trả lời hay nhất nhé!!!
Chúc học tốt!
