Toán Lớp 9: 1. √2????−1=3 2. √5????+9−4=3 3. 2√2????−3=2 4. 2+√????−1=3 5. 3+√7????+4=8 6. 11−√2????−5=8 7. √????−1=√1−???? 8. √2????−5=√1−???? 9. √36????2+12????+1=2 10.

Question

Toán Lớp 9:  1. √2????−1=3 2. √5????+9−4=3 3. 2√2????−3=2 4. 2+√????−1=3 5. 3+√7????+4=8 6. 11−√2????−5=8 7. √????−1=√1−???? 8. √2????−5=√1−???? 9. √36????2+12????+1=2 10. √36????2+12????+1=7 làm gấp giúp  mình với ạ

maingocquynhnhu2k1 · Answer

1, sqrt{2x-1}=3(x>=1/2) <=>2x-1=9 <=>2x=10 <=>x=5(tm) Vậy x=5 2, sqrt{5x+9}-4=3(x>=-9/5) <=> sqrt{5x+9}=7 <=>5x+9=49 <=>5x=40 <=>x=8(tm) Vậy x=8 3, 2 sqrt{2x-3}=2(x>=3/2) <=> sqrt{2x-3}=1 <=>2x-3=1 <=>2x=4 <=>x=2(tm) Vậy x=2 4, 2+ sqrt{x-1}=3(x>=1) <=> sqrt{x-1}=1 <=>x-1=1 <=>x=2 Vậy x=2 5, 3+ sqrt{7x+4}=8(x>=-4/7) <=> sqrt{7x+4}=5 <=>7x+4=25 <=>7x=21 <=>x=3(tm) Vậy x=3 6, 11- sqrt{2x-5}=8(x>=5/2) <=> sqrt{2x-5}=3 <=>2x-5=9 <=>2x=14 <=>x=7(tm) Vậy x=7 7, sqrt{x-1}= sqrt{1-x} <=>{(x-1>=0),(1-x>=0):} <=>{(x>=1),(x<=1):} =>x=1 Vậy x=1 8, sqrt{2x-5}= sqrt{1-x} <=>{(2x-5>=0),(1-x>=0):} <=>$ begin{cases} 2x≥5 x≤1 end{cases}$ <=>$ begin{cases} x≥ dfrac{5}{2} x≤1 end{cases}$(Vô lý) Vậy ptrình vô nghiệm 9, sqrt{36x^2+12x+1}=2 <=> sqrt{(6x+1)^2}=2 <=>|6x+1|=2 <=>[(6x+1=2),(-6x-1=2):} <=>[(6x=1),(6x=-3):} <=>$ left[ begin{matrix} x= dfrac{1}{6} x= dfrac{-1}{2} end{matrix} right.$ Vậy S={1/6;-1/2} 10, sqrt{36x^2+12x+1}=7 <=> sqrt{(6x+1)^2}=7 <=>|6x+1|=7 <=>[(6x+1=7),(6x+1=-7):} <=>[(6x=6),(6x=-8):} <=>$ left[ begin{matrix} x=1 x= dfrac{-4}{3} end{matrix} right.$ Vậy S={1;-4/3}