Algebra · real student question

Solve the equation x^2 - 2 sqrt(3) = 0.

Question

Solve

x223=0x^2-2\sqrt{3}=0

Step-by-step solution

  1. Move the constant across. The constant term happens to be irrational, but that changes nothing about the algebra:

    x2=23x^2=2\sqrt{3}

  2. Check the sign of the right-hand side. 233.4641>02\sqrt3\approx 3.4641>0, so real solutions exist. (Had the constant been negative, x2x^2 would have had to be negative and there would be no real root.)

  3. Take square roots with both signs.

    x=±23x=\pm\sqrt{2\sqrt{3}}

  4. Rewrite the nested radical with fractional exponents. This is the tidiest exact form:

    23=(231/2)1/2=21/231/4=234\sqrt{2\sqrt3}=\left(2\cdot 3^{1/2}\right)^{1/2}=2^{1/2}\,3^{1/4}=\sqrt{2}\,\sqrt[4]{3}

    Numerically 21.41421\sqrt2\approx 1.41421 and 341.31607\sqrt[4]3\approx 1.31607, giving x±1.8612x\approx\pm 1.8612.

  5. Verify by squaring back. 1.861223.46411.8612^2\approx 3.4641 and 233.46412\sqrt3\approx 3.4641 \checkmark. The two roots are exact opposites, as always for an equation of the form x2=kx^2=k.

Answer

x=±23=±234±1.8612x=\pm\sqrt{2\sqrt{3}}=\pm\sqrt{2}\,\sqrt[4]{3}\approx\pm 1.8612

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