ĐKXĐ: x≥0
√x+√2x+1=2
Bình phương 2 vế:
⇒x+2√x(2x+1)+2x+1=4
⇔x+2√2x2+x+2x+1=4
⇔3x+2√2x2+x+1=4
⇔2√2x2+x=3−3x
Bình phương 2 vế:
⇒4(2x2+x)=9−18x+9x2
⇔8x2+4x=9−18x+9x2
⇔8x2+4x−9+18x−9x2=0
⇔x2−22x+9=0
⇔x2−22x+121=−9+121
⇔(x−11)2=112
∘x−11=4√7
⇔x=4√7+11 (TM)
∘x−11=−4√7
⇔x=−4√7+11 (L)
Vậy S={4√7+11}
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