Đáp án:
`1a,S={10/9}`
`b,S={7/2}`
`c,S={2/15}`
`d,S={-11/25}`
`2a,A=S^2-2P`
`b,B=S(S-P)`
`c,C=(S-2P)^2-2P^2`
Giải thích các bước giải:
`1a,(x-1)^3+(2-x)(4+2x+x^2)+3x(x+2)=17`
`<=>(x-1)(x^2-2x+1)+8+4x+2x^2+3x^2+6x=17`
`<=>x^3-3x^2+3x-1+8-x^3+3x^2+6x=17`
`<=>9x=10`
`<=>x=10/9`
`b,(x + 2) (x^2 - 2x + 4) - x(x^2 -2) = 15.`
`<=>x^3-2x^2+4x+2x^2-4x+8-x^3+2x=15`
`<=>2x+8=15`
`<=>2x=7`
`<=>x=7/2`
`c, (x - 3)^3 - (x - 3)(x^2 + 3x + 9) + 9(x + 1)^2 = 15`
`<=>x^3+45x-18-x^3-3x^2-9x+3x^2+9x+27=15`
`<=>45x+9=15`
`<=>45x=6`
`<=>x=2/15`
`d, x(x - 5)(x + 5) - (x + 2)(x^2 - 2x + 4) = 3`
`<=>x^3-25x-x^3+2x^2-4x-2x^2+4x-8=3`
`<=>-25x=11`
`<=>x=-11/25`
`2a,A= (a+b)^2-2ab`
`=S^2-2P`
`b,B=(a+b)(a^2-ab+b^2)`
`=S(S-P)`
`c,C= (a^2+b^2)^2-2a^2b^2`
`=(S-2P)^2-2P^2`