Question

cho P(x)=x³-2x+1; Q(x)=2x²-2x³+x-5

tính a) P(x)+Q(x); b) P(x)-Q(x)

Answer 1

P(x)+Q(x)=(x\(^3\)-2x+1)+(2x\(^2\)-2x\(^3\)+x-5)

=x\(^3\)-2x+1+2x\(^2\)-2x\(^3\)+x-5

= -x\(^3\)+2x\(^2\)-x-4

P(x)-Q(x)=(x\(^3\)-2x+1)+(2x\(^2\)-2x\(^3\)+x-5)

=x\(^3\)-2x+1-2x\(^2\)+2x\(^3\)-x+5

=3x\(^3\)-2x\(^2\)-3x+6

Answer 2

a) P(x) + Q(x) = x³ - 2x + 1 + 2x² - 2x³ + x - 5 = - x³ + 2x² - x - 4

b) P(x) - Q(x) = x³ - 2x + 1 - (2x² - 2x³ + x - 5) = x³ - 2x + 1 - 2x² + 2x³ - x + 5 = 3x³ - 2x² - 3x + 6