Summer Clouds moderators
27/11/2017 at 10:31-
Nguyễn Hiền 29/11/2017 at 08:41
2 x 2 + 2 y 2 - 4 x + 2 y - 172x2+2y2-4x+2y-17
= ( 2 x 2 - 4 x + 2 ) + ( 2 y 2 + 2 y ) - 19=(2x2-4x+2)+(2y2+2y)-19
= 2 ( x - 1 ) 2 + 2 ( y 2 + y ) - 19=2(x-1)2+2(y2+y)-19 ( 1 )(1)
Thay x = 3, y = -2 ta có:
( 1 ) = 2 ( 3 - 1 ) 2 + 2 ( 2 2 - 2 ) - 19(1)=2(3-1)2+2(22-2)-19
= 2,2 2 + 2,2 - 19=2.22+2.2-19
= 8 + 4 - 19=số 8+4-19
= - 7=-7
0
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Nguyễn Thị Hải 27/11/2017 at 11:20
\(2x^2+2y^2-4x+2y-17\)
\(=\left(2x^2-4x+2\right)+\left(2y^2+2y\right)-19\)
\(=2\left(x-1\right)^2+2\left(y^2+y\right)-19\) \(\left(1\right)\)
Thay x=3;y=-2 ta có:
\(\left(1\right)=2\left(3-1\right)^2+2\left(2^2-2\right)-19\)
\(=2.2^2+2.2-19\)
\(=8+4-19\)
\(=-7\)