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bài a) bn trên đã dẫn link cho bn r
bài b)
Đặt x-y=a;y-z=b;z-x=c
\(=>a+b+c=x-y+y-z+z-x=0\)
\(\left(x-y\right)^3+\left(y-z\right)^3+\left(z-x\right)^3=a^3+b^3+c^3\)
Theo câu a)\(a^3+b^3+c^3-3abc=\left(a+b+c\right)\left(a^2+b^2+c^2-ab-bc-ac\right)=0\) (do a+b+c=0)
\(=>a^3+b^3+c^3=3abc=>\left(x-y\right)^3+\left(y-z\right)^3+\left(z-x\right)^3=3\left(x-y\right)\left(y-z\right)\left(z-x\right)\)
a) Ta có :
\(a^3+b^3+c^3-3abc\)
\(\Rightarrow\left(a+b\right)^3-3ab\left(a+b\right)+c^3-3abc\)
\(\Rightarrow\left(a+b+c\right)\left[\left(a+b^2\right)-\left(a+b\right)c+c^2\right]-3ab\left(a+b+c\right)\)
\(\Rightarrow\left(a+b+c\right)\left(a^2+b^2+c^2-ab-bc-ca\right)\)
P/s tham khảo nha
hok tốt
(a-b)3 + (b-c)3 + (c-a)3
=a3 - 3a2b + 3ab2- b3 + b3 - 3b2c + 3bc2- c3 + c3 - 3c2a + 3ca2- a3
=(-3a2b) + 3ab2 - 3b2c + 3bc2 - 3c2a +3ca2
=(-3a2b) + 3(ab2 - b2c + bc2 - c2a + ca2)
=(-3a2b) + 3[ab2 - b(bc - c2) - c(ca - a2)]
a) \(4a^3b^3c^2x+12a^3b^4c^2-16a^4b^5cx\)
\(=4a^3b^3c\left(cx+3bc-4ab^2x\right)\)
b) \(\left(b-2c\right)\left(a-b\right)-\left(a+b\right)\left(2c-b\right)\)
\(=\left(b-2c\right)\left(a-b+a+b\right)=2a\left(b-2c\right)\)
c) \(3a\left(a+5\right)-2\left(5+a\right)=\left(a+5\right)\left(3a-2\right)\)
d) \(\left(x+1\right)^2-3\left(x+1\right)=\left(x+1\right)\left(x+1-3\right)\)
a) Áp dụng hằng đẳng thức (x + y)3 = x3 + y3 + 3xy(x + y) ta có:
(a + b + c)3 - a3 - b3 - c3 = [(a + b) + c]3 - a3 - b3 - c3
= (a + b)3 + c3 + 3(a + b)c(a + b + c) - a3 - b3 - c3
= a3 + b3 + 3ab(a + b) + c3 + 3c(a + b)(a + b + c) - a3 - b3 - c3
= 3(a + b)(ab + ac + bc + c2) = 3(a + b)[a(b + c) + c(b + c)]
= 3(a + b)(b + c)(a + c)
Ta có : x3 + 2x2 + x
= x3 + x2 + x2 + x
= x2(x + 1) + x(x + 1)
= (x2 + x) (x + 1)
= x(x + 1)(x + 1)
nhân tung \(\left(a^2-b\right)\left(b^2-c\right)\left(c^2-a\right)\) ra đề rồi viết ngược lại =.=
\(a^3+b^3+c^3-3abc\)
\(=a^3+3ab\left(a+b\right)+b^3+c^3-3abc-3ab\left(a+b\right)\)
\(=\left(a+b\right)^3+c^3-3ab\left(a+b+c\right)\)
\(=\left(a+b+c\right)\left(a^2+2ab+b^2-ab-ac+c^2\right)-3ab\left(a+b+c\right)\)
\(=\left(a+b+c\right)\left(a^2+b^2+c^2-ab-bc-ca\right)\)
Chúc bạn học tốt nha!!
\(a^3+b^3+c^3-3abc\)
\(=\left(a+b\right)^3-3ab\left(a+b\right)+c^3-3ab\)
\(=\left[\left(a+b\right)+c\right]\left[\left(a+b\right)^2-\left(a+b\right)c+c^2\right]-3ab\left(a+b+c\right)\)
\(=\left(a+b+c\right)\left(a^2+2ab+b^2-ac-bc+c^2-3ab\right)\)
\(=\left(a+b+c\right)\left(a^2+b^2+c^2-ac-bc-ab\right)\)
\(=a^3b-a^3c+b^3c-ab^3+c^3a-bc^3\)
\(=\left(a^3b-ab^3\right)+\left(a^3c-ac^3\right)+\left(b^3c-bc^3\right)\)
\(=ab\left(a^2-b^2\right)+ac\left(a^2-c^2\right)+bc\left(b^2-c^2\right)\)
chị làm CTV đi chị .-.