Đáp án + Giải thích các bước giải:
a)
`A(x)=2f(x)+g(x)=2(x^3 - 2x^2 + 3x+1)+ x^3 + x - 1`
`<=>A(x)=2x^3 - 4x^2 + 6x+2+ x^3 + x - 1`
`<=>A(x)=(2x^3+ x^3) - 4x^2 + (6x+ x)+(2 - 1)`
`<=>A(x)=3x^3- 4x^2 +7x+1`
b)
`2B(x)+f(x)=h(x)`
`<=>2B(x)=h(x)-f(x)`
`<=>B(x)=(h(x)-f(x)):2`
`<=>B(x)=[(2x^2 - 1)-(x^3 - 2x^2 + 3x+1)]:2`
`<=>B(x)=[2x^2 - 1-x^3+2x^2-3x-1]:2`
`<=>B(x)=[(2x^2+2x^2) - (1+1)-x^3-3x]:2`
`<=>B(x)=[4x^2-2-x^3-3x]1/2`
`<=>B(x)=2x^2-1-1/2 x^3-3/2x`
c)
TH1: Đề: `C(x)=2g(x) = 3h(x)`
`C(x)=2g(x) = 3h(x)`
`<=>C(x)=3h(x)`
`<=>C(x)=3(2x^2 - 1)`
`<=>C(x)=6x^2 -3`
TH2: Đề: `C(x)=2g(x)+3h(x)`
`C(x)=2g(x)+3h(x)`
`<=>C(x)=2(x^3 + x - 1)+3(2x^2 - 1)`
`<=>C(x)=2x^3 + 2x - 2+6x^2 - 3`
`<=>C(x)=2x^3 + 2x +6x^2- (2 +3)`
`<=>C(x)=2x^3 + 2x +6x^2- 5`
