请教2个数学问题

zasdzccUID: 173579

A circular pizza is sliced into 12 equal slices.Doug cuts each slice from the center to the edge in equal parts.If Doug eats 2 slices,what is the sum of the degree measures of the slices he eats?
A) 20
B) 60
C) 120
D) 220
E) 240
) X3 b; i" n0 T7 W( X% aAnswer:B Why?[/SIZE]
7 u1 t$ _% o9 \: Z+ U2 O' a! M
8 Z+ a+ v2 n: S- b! yIf the square root of (36x^2+24xy+4y^2) equal to the square root of (9x^2+54xy+81y^2),then which of the following expressions could be equal to y?
A) y=-2x
2 _3 D: x& b$ y' }B) y=-9x/11
% z' D# G) r, ^/ PC) y=3x/7
D) y=9x/11
E) y=3x
Answer:C Why?[/SIZE]

上杉和也UID: 194375

1）圆周360度
  ]8 c6 S& P* f. C# B9 c360/12*2=60
  T: y$ r) k2 C
2）36x^2+24xy+4y^2=9x^2+54xy+81y^2
27x^2-30xy-77y^2=0
(3x-7y)(9x+11y)=0
y=3x/7 or y=-9x/11

zasdzccUID: 173579

多谢

cameoUID: 2160222

y=3x/7 or y=-9x/11 [/quote]
* {! g* o; [- w! ^为何不选B?

princessWXUID: 2209296

Is there any can tell why?!
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+ [$ H$ j& S5 uThis question belong to which year??