Question

Dạng tìm GTNN-GTLN
vd:x^2+2x+3=x^2+2x.1+1+2=x+1)^2+2

Answer 1

6:

=y^2+y+1/4-1/4

=(y+1/2)^2-1/4>=-1/4

Dấu = xảy ra khi y=-1/2

7:

=5(x^2+4/5x-3/5)

=5(x^2+2*x*2/5+4/25-19/25)

=5(x+2/5)^2-19/5>=-19/5

Dấu = xảy ra khi x=-2/5

8: =7(x^2-12/7x-6/7)

=7(x^2-2*x*6/7+36/49-78/49)

=7*(x-6/7)^2-78/7>=-78/7

Dấu = xảy ra khi x=6/7

9: =x^2-2x+1+y^2-4y+4

=(x-1)^2+(y-2)^2>=0

Dấu = xảy ra khi x=1 và y=2

10: =x^2-x+1/4+1/4

=(x-1/2)^2+1/4>=1/4

Dấu = xảy ra khi x=1/2