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a)\(P=\left(5x-1\right)+2\left(1-5x\right)\left(4+5x\right)+\left(5x+4\right)\)
\(P=5x-1+5x+4+\left(2-10x\right)\left(4+5x\right)\)
\(P=10x+3+8+10x-40x-50x^2\)
\(P=-20x+11-50x^2\)
b)\(Q=\left(x-y\right)^3+\left(y+x\right)^3+\left(y-x\right)^3-3xy\left(x+y\right)\)
\(Q=x^3-3x^2y+3xy^2-y^3+y^3+3y^2x+3yx^2+x^3+y^3-3y^2x+3yx^2-x^3-3x^2y+3xy^2\)
\(Q=x^3+y^3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)
P=(5x−1)+2(1−5x)(4+5x)+(5x+4)2
P=(5x−1)2+2(1−5x)(4+5x)+(5x+4)2−(5x−1)2
P=(5x−1+5x+4)2−(5x−1)2
P=(5x−1+5x+4−5x+1)(5x−1+5x+4+5x−1
b)
Q= (x-y)^3 + (x+y)^3 + (y-x)^3 - [3xy(x+y)]
(x-y)^3 = x^3 - 3x^2y + 3xy^2 - y^3
(x+y)^3 = x^3 + 3x^2y + 3xy^2 + y^3
(y-x)^3 = y^3 - 3xy^2 + 3x^2y - x^3
Q= (2x^3 + 6xy^2) + (y^3 - 3xy^2 + 3x^2y - x^3) - [3xy(x+y)]
= (x^3 + 3xy^2 + 3x^2y + y^3) - 3x^2y - 3xy^2
Q= x^3 + y^3
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
rút gọn các biểu thức sau .
a) P= (5x-1)+2(1-5x)(4+5x)+(5x+4)2
b) Q = (x-y )3 + (y+x)3+(y-x)3-3xy(x+y)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) P= (5x-1)+2(1-5x)(4+5x)+(5x+4)2
P = (5x-1)2 + 2(1 - 5x)(4 + 5x)+ (5x + 4)2 - (5x - 1)2
P = (5x - 1 + 5x + 4)2 - (5x - 1)2
P = (5x - 1 + 5x + 4 - 5x + 1) (5x - 1 + 5x + 4 + 5x - 1)
b) làm tương tự nhé!! kết quả: Q = x3 + y3
t i c k nha!! 5364574674675678568585785789769647568585
a) P = (5x - 1) + [(-2).(-1).(1-5x).(4+5x)] + (5x+4)^2
= (5x - 1).[(-1)-2.(-1).(4+5x)] + (25x^2+40x+16)
= [(5x - 1).(10x + 7)] + (25x^2+40x+16)
= 50x^2 +35x - 10x - 7 + 25x^2+40x+16
= 75x^2 + 65x -9
b) Q = (x-y)^3 + (x+y)^3 + (y-x)^3 - [3xy(x+y)]
Xét (x-y)^3 = x^3 - 3x^2y + 3xy^2 - y^3 = x^3 + 3x^2y + 3xy^2 + y^3 = y^3 - 3xy^2 + 3x^2y - x^3
Do đó Q = (2x^3 + 6xy^2) + (y^3 - 3xy^2 + 3x^2y - x^3) - [3xy(x+y)]
= (x^3 + 3xy^2 + 3x^2y + y^3) - 3x^2y - 3xy^2
= x^3 + y^3
a, P=(5x-1)+2(1-5x)(4+5x)+(5x+4)
=5x-1+2.(4-15x-5x2)+5x+4
=5x-1+8-30x-10x2+5x+4
=-10x2-20x+11
b,Q=(x-y)^3 +(y+x)^3+ (y-x)^3 -3xy(x+y)
=x3-3x2y+3xy2-y3+y3+3x2y+3xy2+x3+y3-3y2x+3yx2-x3-3x2y-3xy2
=x3+y3