Đề sai sửa lại là
(7a - 3b + 2c ) (7a - 3b - 2c ) = (3a - 7b )2
Ta có VT = ( 7a - 3b)2 - 4c2 = (3a - 7b )2 + 40a2 - 40b2 - 4c2 = (3a - 7b )2 = VP
Cho 10a^2=10b^2+c^2. Chứng minh rằng (7a-3b+2c)(7a-3b-2c)=(3a-7b)^2
Cho 10a^2=10b^2+c^2. Chứng minh rằng (7a-3b+2c)(7a-3b-2c)=(3a+b)^2
Cho 10a^2 = 10b^2 + c^2
CMR: ( 7a - 3b + 2c )( 7a - 3b - 2c ) - (3a - 7b )^2
Cho 10a^2 = 10b^2 + c^2
CMR: ( 7a - 3b + 2c )( 7a - 3b - 2c ) - (3a - 7b )^2
cho: 10a^2=10b^2+c
tinh (7a-3b+2c).(7a-3b-2c)=(3a-7b)^2
Cho 10a^2= 10b^2-c^2
CMR ( 7a-3b-2c)(7a+3b+2c) = (3a-7b)^2
chứng minh rằng 2 đa thức : 2bc(b+2c+2ac(c-2a)-2ab(a+2b-7a)=(b+2c)(c-2a)a+2b
Cho a>b>c>0. Chứng minh rằng :
\(a^3b^2+b^3c^2+c^3a^2>a^2b^3+b^2c^3+c^2a^3\)
Cho\(\dfrac{a}{b}\)=\(\dfrac{c}{d}\). Chứng minh:
a,\(\dfrac{ab}{cd}\)=\(\dfrac{a^2-b^2}{c^2-d^2}\)
b,\(\dfrac{5a+3b}{5a-3b}\)=\(\dfrac{5c+3d}{5c-3d}\)
c,\(\dfrac{7a^2+3ab}{11a^2-8b^2}\)=\(\dfrac{7c^2+3cd}{11c^2-8d^2}\)
