CMR: x^2 - 10x + 30 > 0 với mọi x

cmr A=n3(n2-7)2-36n chia hết cho 5040

Cho : a+2b+3c=0

a2+4b2+9c2=20

Tính : a4+16b4+81c4

Cho a + b + c = 0

CM: a^3 + b^3 + c^3 = 3abc

Tính nhanh :

978^2+22^2+978*44

Tính :

x^2+6x+9 với x=997

16a2+25b2+40ab

giải pt sau

g) 11+8x-3=5x-3+x

h)4-2x+15=9x+4-2x

g)\(\dfrac{3x+2}{2}-\dfrac{3x+1}{6}=\dfrac{5}{3}+2x\)

h)\(\dfrac{x+4}{5}-x+4=\dfrac{4x+2}{5}-5\)

i)\(\dfrac{4x+3}{5}-\dfrac{6x-2}{7}=\dfrac{5x+4}{3}+3\)

k) \(\dfrac{5x+2}{6}-\dfrac{8x-1}{3}=\dfrac{4x+2}{5}-5\)

m) \(\dfrac{2x-1}{5}-\dfrac{x-2}{3}=\dfrac{xx+7}{15}\)

n)\(\dfrac{1}{4}\left(x+3\right)=3-\dfrac{1}{2}\left(x+1\right)-\dfrac{1}{3}\left(x+2\right)\)

p)\(\dfrac{x}{3}-\dfrac{2x+1}{6}=\dfrac{x}{6}-x\)

q)\(\dfrac{2+x}{5}-0,5x=\dfrac{1-2x}{4}+0,25\)

Giải phương trình sau bàng cách đưa về dạng ax+b=0

a) 3x-2=2x-3

b) 3-4y+24+6y=y+27+3y

c)7-2x=22-3x

d) 8x-3=5x+12

e)x-12+4x=25+2x-1

f)x+2x+3x-19=3x+5

Rút gọn :

D= \(\left(x+7\right)^2-\left(x-7\right)^2\)

Rút gọn :

A = ( x + y + 3 )2 - ( x2 + y2 + 9 )

B = ( 5x - 2 ) ( 5x + 2 ) - ( 5x - 1)2

C = 1002 + 982 + 962 + --. + 22 - 992 + 972 + 952 + --.+ 12