Đáp án:
= 2x2 + 4xyz – y + 2.
= -8x2 + 2xyz + 10xy + y – 4.
= 8x2 – 2xyz – 10xy – y + 4.
Bài 2
a)
Vậy P = 4y2 – 1.
b)
Vậy Q = 7x2 – 4xyz + xy + 5.
Giải thích các bước giải:
Trả lời:
M + N = (3xyz – 3x2 + 5xy – 1) + (5x2 + xyz – 5xy + 3 – y)
= – 3x2 + 5x2 + 3xyz + xyz + 5xy – 5xy – y – 1 + 3
= 2x2 + 4xyz – y + 2.
M – N = (3xyz – 3x2 + 5xy – 1) – (5x2 + xyz – 5xy + 3 – y)
= 3xyz – 3x2 + 5xy – 1 – 5x2 – xyz + 5xy – 3 + y
= -3x2 – 5x2 + 3xyz – xyz + 5xy + 5xy + y – 1 – 3
= -8x2 + 2xyz + 10xy + y – 4.
N – M = (5x2 + xyz – 5xy + 3 – y) – (3xyz – 3x2 + 5xy – 1)
= 5x2 + xyz – 5xy + 3 – y – 3xyz + 3x2 – 5xy + 1
= 5x2 + 3x2 + xyz – 3xyz – 5xy – 5xy – y + 3 + 1
= 8x2 – 2xyz – 10xy – y + 4.
a)P + (x2– 2y2) = x2 – y2 + 3y2 – 1
P = (x2 – y2 + 3y2 – 1) – (x2 – 2y2)
P = x2 – y2 + 3y2 – 1 – x2 + 2y2
P = x2 – x2 – y2 + 3y2 + 2y2 – 1
P = 4y2 – 1.
Vậy P = 4y2 – 1.
b)Q – (5x2– xyz) = xy + 2x2 – 3xyz + 5
Q = (xy + 2x2 – 3xyz + 5) + (5x2 – xyz)
Q = xy + 2x2 – 3xyz + 5 + 5x2 – xyz
Q = 7x2 – 4xyz + xy + 5
Vậy Q = 7x2 – 4xyz + xy + 5.
Thấy hay thì cho mình xin 5 sao nha
