P(x)=-5x^4+6x^3-2x^2-x+7
Q(x)=x^4-8x^3-3x^2-7x-1
tính :a,P(x)-Q(x)
b,P(x)+Q(x)
c,Q(x)-P(x)
0 bình luận về “P(x)=-5x^4+6x^3-2x^2-x+7
Q(x)=x^4-8x^3-3x^2-7x-1
tính :a,P(x)-Q(x)
b,P(x)+Q(x)
c,Q(x)-P(x)”
Đáp án:
a.\(-6x^{4}+14x^{3}+x^{2}+6x+8\)
b. \(-4x^{4}-2x^{3}-5x^{2}-8x+6\)
c. \(6x^{4}-14x^{3}-x^{2}-6x-8\)
Giải thích các bước giải:
a. \(P(x)-Q(x)=-5x^{4}+6x^{3}-2x^{2}-x+7-x^{4}+8x^{3}+3x^{2}+7x+1=(-5x^{4}-x^{4})+(6x^{3}+8x^{3})+(-2x^{2}+3x^{2})+(-x+7x)+(7+1)=-6x^{4}+14x^{3}+x^{2}+6x+8\)
b. \(P(x)+Q(x)=-5x^{4}+6x^{3}-2x^{2}-x+7+x^{4}-8x^{3}-3x^{2}-7x-1=-4x^{4}-2x^{3}-5x^{2}-8x+6\)
c. \(Q(x)-P(x)=x^{4}-8x^{3}-3x^{2}-7x-1-(-5x^{4}+6x^{3}-2x^{2}-x+7)=(x^{4}+5x^{4})+(-8x^{3}-6x^{3})+(-3x^{2}+2x^{2})+(-7x+x)+(-1-7)=6x^{4}-14x^{3}-x^{2}-6x-8\)
Đáp án:
a.\(-6x^{4}+14x^{3}+x^{2}+6x+8\)
b. \(-4x^{4}-2x^{3}-5x^{2}-8x+6\)
c. \(6x^{4}-14x^{3}-x^{2}-6x-8\)
Giải thích các bước giải:
a. \(P(x)-Q(x)=-5x^{4}+6x^{3}-2x^{2}-x+7-x^{4}+8x^{3}+3x^{2}+7x+1=(-5x^{4}-x^{4})+(6x^{3}+8x^{3})+(-2x^{2}+3x^{2})+(-x+7x)+(7+1)=-6x^{4}+14x^{3}+x^{2}+6x+8\)
b. \(P(x)+Q(x)=-5x^{4}+6x^{3}-2x^{2}-x+7+x^{4}-8x^{3}-3x^{2}-7x-1=-4x^{4}-2x^{3}-5x^{2}-8x+6\)
c. \(Q(x)-P(x)=x^{4}-8x^{3}-3x^{2}-7x-1-(-5x^{4}+6x^{3}-2x^{2}-x+7)=(x^{4}+5x^{4})+(-8x^{3}-6x^{3})+(-3x^{2}+2x^{2})+(-7x+x)+(-1-7)=6x^{4}-14x^{3}-x^{2}-6x-8\)
`a,P(x)-Q(x)=(-5x^4+6x^3-2x^2-x+7)-(x^4-8x^3-3x^2-7x-1)`
`=-5x^4+6x^3-2x^2-x+7-x^4+8x^3+3x^2+7x+1`
`=-(5x^4+x^4)+(6x^3+8x^3)+(-2x^2+3x^2)+(-x+7x)+(7+1)`
`=-6x^4+14x^3+x^2+6x+8`
`b,P(x)+Q(x)=(-5x^4+6x^3-2x^2-x+7)+(x^4-8x^3-3x^2-7x-1)`
`=-5x^4+6x^3-2x^2-x+7+x^4-8x^3-3x^2-7x-1`
`=(-5x^4+x^4)+(6x^3-8x^3)-(2x^2+3x^2)-(x+7x)+(7-1)`
`=-4x^4-2x^3-5x^2-8x+6`
`c,Q(x)-P(x)=-(P(x)-Q(x))`
`=-(-6x^4+14x^3+x^2+6x+8)=6x^4-14x^3-x^2-6x-8`