`a) h(x)=f(x)+g(x)`
`=>h(x)=(7x^{5}+x^{4}-2x^{3}+4)+(x^{4}+6x^{3}-4x^{2}+2x-1)`
`=7x^{5}+x^{4}-2x^{3}+4+x^{4}+6x^{3}-4x^{2}+2x-1`
`=7x^{5}+(x^{4}+x^{4})+(-2x^{3}+6x^{3})-4x^{2}+2x+(4-1)`
`=7x^{5}+2x^{4}+4x^{3}-4x^{2}+2x+3`
`b) h(x)=f(x)-g(x)`
`=>h(x)=(7x^{5}+x^{4}-2x^{3}+4)-(x^{4}+6x^{3}-4x^{2}+2x-1)`
`=7x^{5}+x^{4}-2x^{3}+4-x^{4}-6x^{3}+4x^{2}-2x+1`
`=7x^{5}+(x^{4}-x^{4})+(-2x^{3}-6x^{3})+4x^{2}-2x+(4+1)`
`=7x^{5}-8x^{3}+4x^{2}-2x+5`
`c) f(x)+h(x)=0`
`=>h(x)=-f(x)=-(7x^{5}+x^{4}-2x^{3}+4)`
`=>h(x)=-7x^{5}-x^{4}+2x^{3}-4`
`d) g(x)-h(x)=0`
`=>h(x)=g(x)=x^{4}+6x^{3}-4x^{2}+2x-1`
`=>h(x)=x^{4}+6x^{3}-4x^{2}+2x-1`
$\text{Xin hay nhất }$
