bai1; giai pt:$ C^{1}_{x} + 6C^{2}_{x} + 6C^{3}_{x} = 9x^{2} - 14$

bai2" rut gon:$ C^{0}_{5}.C^{k}_{n} + C^{1}_{5}.C^{k - 1}_{n} +.....+ C^{5}_{5}.C^{k - 5}_{n}$. Biet:
                                                   $C^{n}_{n} + C^{n - 1}_{n} + C^{n - 2}_{n}= 79$

cho pt: $sin^{3}x - 5sin^{2}x + 7sinx - m + 1=0$
     a/ tim m de pt co nghiem
     b/ tim m de pt co 5 nghiem $\in (0; \frac{29\pi }{6})$

bai1: cho cac so tu 0>9
a/ co bao nhieu so tu nhien gom 7 chu so khac nhau sao cho luon co mat 2 chu so 2
b/ co bn so tu nhien gom 7 chu so khac nhau sao cho chu so 5 dung chinh giua

bai2: cho 6 nam va 5 nu can thanh lap 1 doi van nghe gom 5 nguoi:
a/ tinh so cach thanh lap doi sao cho co it nhat 1 nam
b/ tinh so cach thanh lap doi sao cho khong it hon 3 nam

cho   $d1: 2x - y=0$
        $d2: x + y -1=0$
        $d3: x - y -1=0$
Lap phuong trinh duong tron co tam thuoc d1 tiep xuc voi d2 cat d3 tai 2 diem phan biet A, B sao cho $AB= 4\sqrt{2}$

giai pt: $3sin3x + 2 + sinx( 3 - 8cosx)= 3cosx$

cho tam giac ABC co M(1;4) la trung diem AB. Phuong trinh duong phan giac trong goc B: x - 2y + 2=0. Phuong trinh duong cao qua C: 3x + 4y - 15=0. Tim toa do cac dinh A,B,C

giai pt: a/  $4cos^{2}x + 3sinx + \sqrt{3}cosx = 3$
          b/ $2cos^{2}(\frac{\pi }{4} - 2x) + \sqrt{3}cos4x= 4cos^{2}x - 1$

giai phuong trinh: $sin3x + cos3x + cosx - sinx = \sqrt{2}cos2x$

           ( Dung cong thuc goc nhan 3 giup minh nha)

Giải các phương trình:
 a) $\sin^2x+\sin^23x=\cos^22x+\cos^24x$
 b) $\sin^6x+\cos^6x=\cos^22x+\dfrac{1}{16}$
 c) $\sin x+\cos x = 0$

giai pt: $2x + 1 + x\sqrt{x^{2} + 2} + (x + 1)\sqrt{x^{2} + 2x + 3} = 0$

bai2: tinh cac gia tri luong giac
a/ $\sin (\frac{-11\pi }{4})$
b/ $ \cot (\frac{21\pi }{4})$
c/ $ cos ( -675 do)$

bai1: trong mat phang voi he truc toa do Oxy, cho duong thang D: x - 3y - 4=0 va 

bai1: giai he phuong trinh: $\left\{ \begin{array}{l} x + y + \sqrt{x^{2}- y^{2}} = 12\\ y\sqrt{x^{2} - y^{2}} = 12 \end{array} \right.$
bai2: tim m de phuong trinh sau co nghiem: $\sqrt[4]{x^{2} + 1} - \sqrt{x} = m$

bai1:  cho E co phuong trinh:$ 3x^{2} + 5y^{2} = 30$
a/ tim toa do cac dinh, toa do cac tieu diem va tam sai cua elip
b/ 1 duong thang d qua tieu diem F2(2,0) cua E song song voi truc tung cat E tai 2 diem A va B. Tinh khoang cach tu A va B toi tieu diem F1

bai2: cho 2 Elip co phuong trinh: $\frac{x^{2}}{9} + \frac{y^{2}}{4} = 1 $ va $ \frac{x^{2}}{10} + y^{2} = 1$
chung minh rang 2 elip cat nhau tai 4 diem va 4 diem do cung nam tren 1 duong tron ma ta se viet duoc phuong tribnh

bai1: cho tam giac ABC co $\frac{c}{b} = \frac{m_{b}}{m_{c}} \neq 1$. chung minh rang
                 $\cot A = \frac{1}{2}(\cot B + \cot C)$

bai2: chung minh rang tam giac ABC deu neu thoa man 1 trong cac dieu kien sau:
a/ $\left\{ \begin{array}{l} \frac{b^{3} + c^{3} - a^{3}}{b + c - a} = a^{2}\\ a = 3b\cos C \end{array} \right.$
b/ $\left\{ \begin{array}{l} \frac{b^{3} + c^{3} - a^{3}}{b + c - a} = a^{2}\\ \frac{1}{\sin B} + \frac{1}{\sin C} = \frac{4}{\sin B + \sin C}\end{array} \right.$

chung minh rang neu A, B, C la 3 goc cua 1 tam giac ABC thi
a/ $\sin \frac{A + B + 3C}{2} = \cos C$
b/ $\cos ( A + B - C) = -\cos 2C$
c/ $\tan \frac{A + B - 2C}{2} = \cot \frac{3C}{2}$