\(2\sqrt{1-x}-\sqrt{x+1}+3\sqrt{1-x^2}=3-x\)

\(2\sqrt{1-x}-\sqrt{1+x}+2\sqrt{\left(1-x\right)\left(1+x\right)}+\sqrt{\left(1-x\right)\left(1+x\right)}=3-x\)

\(2\sqrt{1-x}\left(1-\sqrt{1+x}\right)-\sqrt{1+x}\left(1-\sqrt{1-x}\right)=3-x\)

Tìm C_min

Biết C=(2x+6)²+|y+1|+2019

Vì (2x+6)² \(\ge\) 0 \(\forall\) x

|y+1| \(\ge\) 0 \(\forall\) y

\(\Rightarrow\)(2x+6)²+|y+1| \(\ge\) 0

\(\Rightarrow\)(2x+6)²+|y+1|+2019 \(\ge\) 2019

\(\Rightarrow\)C \(\ge\) 2019

Dấu "=" xảy ra

\(\Leftrightarrow\)2x+6=0          \(\Leftrightarrow\)y+1=0

\(\Leftrightarrow\)2x=-6             \(\Leftrightarrow\)y=-1

\(\Leftrightarrow\)x=-3

Vậy C_min=2019 \(\Leftrightarrow\)x=-3; y=-1

12-13-14-15-16-17-18-19=1+x

(-1)-14-15-16-17-18-19=1+x

(-15)-15-16-17-18-19=1+x

(-30)-16-17-18-19=1+x

(-46)-17-18-19=1+x

(-63)-18-19=1+x

(-63)-(18+19)=1+x

(-63)-37=1+x

(-100)=1+x

              x= (-100)-1

              x=-101

Trl:

\(12-13-14-15-16-17-18-19=1+x\)

\(\Rightarrow-1-13-14-15-16-17-18-19=1+x\)

\(\Rightarrow-15-15-16-17-18-19=1+x\)

\(\Rightarrow-30-16-17-18-19=1+x\)

\(\Rightarrow-46-17-18-19=1+x\)

\(\Rightarrow-63-18-19=1+x\)

\(\Rightarrow-81-19=1-x\)

\(\Rightarrow-100=1+x\)

\(\Rightarrow x=-100-1\)

\(\Rightarrow x=-101\)

Dạng này dùng hệ số bât định làm gì cho mệt?