PTĐTTNT
a/ 3x^2 + 6xy + 3y^2 - 3z^2

b/ xz + yz - 5. ( x + y )

c/ 3x^2 - 5x - 3xy + 5y

d/ x^2 + 4x - 1/25y^2 +4

Tính nhanh

45^2 + 40^2 - 15^2 + 80 . 45

PTĐTTNT

 n^2 + 5n - 6

1 PTĐTTNT 

a/ 2x - 2y - x^2 + 2xy - y^2

b/ x^4 - 2x^2

c/ x^2 - y^2 - 2y - 1

d/ n^2 + 5n - 6

e/ y^2 - y - 6

f/ 5 - 3a^2 + 2a

g/ 3b^2 - 4 +4b

1  PTĐTTNT

a/ -x^3 + 9x^2 - 27x + 27

b/ x^4 - 3x^3 + x^3y - 3x^2y

c/ x^3 + yx^2 + 2x^2y - 9x^3

2 tìm x

x^2 - x = -1/4

1/ PTĐTTNT 

a/ 8x^3 - 1/8

b/ 1/25y^2 - 64x^2

c/ 10x - 25 - x^2 

d/ x^4 + x/27

e/ ( a + b )^3 - ( a - b )^3

Tìm x 

x^2 - x = -1/4

chứng minh 55^n+1 - 55^n chia hết 54 vs n thuộc N

tìm x 

x^3 = 13x