Question

Bài 1

Cho 2 đa thức M= [x+(y-z)-2x]+y+z-(2-x-y)

                         N= x-[x-(y-z)-x]

Tính M+N và M-N

Bài 2

Cho 2 đa thức P= a'2-2ab+3b'2

                        Q= 2a'2-3ab-b'2+(-3a'2+2ab-b'2)

Tính P+Q và P-Q

Answer 1

`#3107.101107`

`1.`

`M = [x+(y-z)-2x]+y+z-(2-x-y)`

`= x + y - z - 2x + y + z - 2 + x + y`

`= (x - 2x + x) + (y + y + y) + (z - z)`

`= 3y`

`N= x-[x-(y-z)-x]`

`= x - (x - y + z - x)`

`= x - (z - y)`

`= x + y - z`

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`M + N = 3y + x + y - z = 4y + x - z`

`M - N = 3y - (x + y - z) = 3y - x - y + z = 2y - x + z`

Answer 2

`2.`

`Q= 2a^2-3ab-b^2+(-3a^2+2ab-b^2)?`

`= 2a^2 - 3ab - b^2 - 3a^2 + 2ab - b^2`

`= (2a^2 - 3a^2) - (3ab - 2ab) - (b^2 + b^2)`

`= -a^2 - ab - 2b^2`

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`P + Q = a^2 - 2ab + 3b^2 - a^2 - ab - 2b^2`

`= (a^2 - a^2) - (2ab + ab) + (3b^2 - 2b^2)`

`= -3ab + b^2`

`P - Q = a^2 - 2ab + 3b^2 - (-a^2 - ab - 2b^2)`

`= a^2 - 2ab + 3b^2 + a^2 + ab + 2b^2`

`= 2a^2 - ab + 5b^2`

Answer 3

Bài 2: 

\(Q=2a^2-3ab-b^2+\left(-3a^2+2ab-b^2\right)\\ =2a^2-3ab-b^2-3a^2+2ab-b^2\\ =-a^2-ab-2b^2\)

\(P+Q=\left(a^2-2ab+3b^2\right)+\left(-a^2-ab-2b^2\right)\\ =a^2-2ab+3b^2-a^2-ab-2b^2\\ =-3ab+b^2\\ P-Q=\left(a^2-2ab+3b^2\right)-\left(-a^2-ab-2b^2\right)\\ =a^2-2ab+3b^2+a^2+ab+2b^2\\ =2a^2-ab+5b^2\)