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Mathematics

In each of the following, determine whether the given numbers are solutions of the given equations or not:

(i) x233x+6=0;3, 23x^2 - 3\sqrt{3}x + 6 = 0; \sqrt{3}, \space -2\sqrt{3}

(ii) x22x4=0;2, 22x^2 - \sqrt{2}x - 4 = 0; -\sqrt{2}, \space 2\sqrt{2}

Quadratic Equations

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Answer

(i) Given,

x233x+6=0x^2 - 3\sqrt{3}x + 6 = 0

Substituting x = 3\sqrt{3} in the LHS of the given equation, we get:

LHS=(3)233×3+6=39+6=99=0=RHS\text{LHS} = (\sqrt{3})^2 - 3\sqrt{3} \times \sqrt{3} + 6 \\[0.5em] = 3 - 9 + 6 \\[0.5em] = 9 - 9 \\[0.5em] = 0 \\[0.5em] = \text{RHS}

3\sqrt{3} is a solution of the given equation

Substituting x = 23-2\sqrt{3} in the LHS of the given equation, we get:

LHS=(23)233×23+6=12+18+6=36\text{LHS} = (-2\sqrt{3})^2 - 3\sqrt{3} \times -2\sqrt{3} + 6 \\[0.5em] = 12 + 18 + 6 \\[0.5em] = 36

RHS\text{RHS}

23-2\sqrt{3} is not a solution of the given equation

Hence, 3\sqrt{3} is a solution of the given equation but 23-2\sqrt{3} is not.

(ii) Given,

x22x4=0x^2 - \sqrt{2}x - 4 = 0

Substituting x = 2-\sqrt{2} in the LHS of the given equation, we get:

LHS=(2)22×(2)4=2+24=0=RHS\text{LHS} = (-\sqrt{2})^2 - \sqrt{2} \times (-\sqrt{2}) - 4 \\[0.5em] = 2 + 2 - 4 \\[0.5em] = 0 \\[0.5em] = \text{RHS}

2-\sqrt{2} is a solution of the given equation

Substituting x = 222\sqrt{2} in the LHS of the given equation, we get:

LHS=(22)22×224=844=88=0=RHS\text{LHS} = (2\sqrt{2})^2 - \sqrt{2} \times 2\sqrt{2} - 4 \\[0.5em] = 8 - 4 - 4 \\[0.5em] = 8 - 8 \\[0.5em] = 0 \\[0.5em] = \text{RHS}

222\sqrt{2} is a solution of the given equation

Hence, 2-\sqrt{2} and 222\sqrt{2} both are solutions of the given equation.

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