Solve the equation 2x+1−x=1\sqrt{2x+1} - \sqrt{x} = 1. Express (23−5)23−2\frac{\left(2\sqrt{3}-5\right)^2}{\sqrt{3}-2} in the form p3+qp\sqrt{3} + q where pp and qq are integers.

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Worked solution

1(a)

1. Rearrange the equation to isolate one of the surds and square both sides.

2x+1=x+1\sqrt{2x+1} = \sqrt{x} + 1
(2x+1)2=(x+1)2(\sqrt{2x+1})^2 = (\sqrt{x} + 1)^2
2x+1=x+2x+12x + 1 = x + 2\sqrt{x} + 1

2. Simplify the equation to isolate the remaining surd.

2x−x+1−1=2x2x - x + 1 - 1 = 2\sqrt{x}
x=2xx = 2\sqrt{x}

3. Square both sides again to remove the remaining surd and solve for $x$.

x2=(2x)2x^2 = (2\sqrt{x})^2
x2=4xx^2 = 4x
x2−4x=0x^2 - 4x = 0
x(x−4)=0x(x - 4) = 0
x=0 or x=4x = 0 \text{ or } x = 4

4. Check the solutions in the original equation to reject any extraneous roots.

Substitute x=0x = 0:
LHS =2(0)+1−0=1−0=1=RHS= \sqrt{2(0)+1} - \sqrt{0} = 1 - 0 = 1 = \text{RHS}
Substitute x=4x = 4:
LHS =2(4)+1−4=9−2=3−2=1=RHS= \sqrt{2(4)+1} - \sqrt{4} = \sqrt{9} - 2 = 3 - 2 = 1 = \text{RHS}
Both solutions are valid.

Answer

x=0x = 0 or x=4x = 4

1(b)

1. Expand the numerator

(23−5)2=(23)2−2(23)(5)+52\left(2\sqrt{3}-5\right)^2 = (2\sqrt{3})^2 - 2(2\sqrt{3})(5) + 5^2
=12−203+25= 12 - 20\sqrt{3} + 25
=37−203= 37 - 20\sqrt{3}

2. Multiply numerator and denominator by the conjugate of the denominator

37−2033−2=(37−203)(3+2)(3−2)(3+2)\frac{37 - 20\sqrt{3}}{\sqrt{3}-2} = \frac{(37 - 20\sqrt{3})(\sqrt{3}+2)}{(\sqrt{3}-2)(\sqrt{3}+2)}

3. Expand the new numerator and simplify the denominator

Denominator: (3)2−22=3−4=−1(\sqrt{3})^2 - 2^2 = 3 - 4 = -1
Numerator: 373+74−20(3)−40337\sqrt{3} + 74 - 20(3) - 40\sqrt{3}
=373+74−60−403= 37\sqrt{3} + 74 - 60 - 40\sqrt{3}
=14−33= 14 - 3\sqrt{3}

4. Simplify to the final form

14−33−1=−14+33\frac{14 - 3\sqrt{3}}{-1} = -14 + 3\sqrt{3}
=33−14= 3\sqrt{3} - 14

Answer

33−143\sqrt{3} - 14

AI analysis — may contain mistakes.

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