Ta có : P=t2+3−4t2P=t2+3−4t2
=> P=t2−4t+4−12=(t−2)22−12P=t2−4t+4−12=(t−2)22−12
Ta thấy : (t−2)2≥0∀x(t−2)2≥0∀x
=> (t−2)22−12≥−12∀x(t−2)22−12≥−12∀x
Vậy MinP=−12MinP=−12 <=> t−2=0t−2=0
<=> t=2(TM)t=2(TM)
<=> 2x−3−−−−−√=22x−3=2
<=> 2x−3=42x−3=4
<=> 2x=72x=7
<=> x=72(TM) bài này mk lm r
HỌC TỐT