X6− 5 X2+ = 2 0 ; 2) 312 − + X 314 + = X 2CÂU II.(5Đ) − + − + −2( )...
1) x
6
− 5 x
2
+ = 2 0 ; 2)
3
12 − + x
3
14 + = x 2
Câu II.(5đ)
− + − + −
2
( )
2
( )
2
( )
+ =
Cho tam ∆ ABC thỏa mãn:
sin cos a p a b p b c p c
A A
abc
Chứng minh ∆ ABC vuông:
Câu III.(4đ)
Tìm k ∈ ¥ sao cho:
C14
k
+C14
k
+
2
=2C14
k
+
1