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Question 1 Find the nature of the roots of the following quadratic equations. If the real roots exist, find them:
(i) $2x^{2} – 3x + 5$ = 0

(ii) $3x^{2} – 4\sqrt{3}x + 4$ = 0

(iii) $2x^{2} – 6x + 3$ = 0
Solution:

(i) Given,$2x^{2} – 3x + 5$ = 0

Comparing the equation with $ax^{2} + bx + c $= 0, we get

a = 2, b = -3 and c = 5

We know, discriminant = $b^{2} – 4ac$

= $( – 3)^{2}– 4 (2) (5)$ = 9 – 40

= – 31

As you can see, $b^{2} – 4ac$ < 0

Therefore, no real root is possible for the given equation, $2x^{2}$ – 3x + 5 = 0.

(ii) $3x^{2} – 4\sqrt{3}x$ + 4 = 0

Comparing the equation with $ax^{2}$ + bx + c = 0, we get

a = 3, b = $-4\sqrt{3}$ and c = 4

We know, Discriminant = $b^{2}$ – 4ac

= $(-4\sqrt{3})^{2}$ – 4(3)(4)

= 48 – 48 = 0

As $b^{2} – 4ac$ = 0,

Real roots exist for the given equation, and they are equal to each other.

Hence, the roots will be $\dfrac{–b}{2a}$ and $\dfrac{–b}{2a}$.

$\dfrac{–b}{2a}$

=$ \dfrac{-(-4\sqrt{3})}{2×3}$

= $\dfrac{4\sqrt{3}}{6} $

= $\dfrac{2\sqrt{3}}{3}$

= $\dfrac{2}{\sqrt{3}}$

Therefore, the roots are $\dfrac{2}{\sqrt{3}}$ and $\dfrac{2}{\sqrt{3}}$

(iii) $2x^{2} – 6x + 3$ = 0

Comparing the equation with $ax^{2} + bx + c$ = 0, we get

a = 2, b = -6, c = 3

As we know, discriminant = $b^{2} – 4ac$

= $(-6)^{2}$ – 4 (2) (3)

= 36 – 24 = 12

As$ b^{2} – 4ac$ > 0,

Therefore, there are distinct real roots that exist for this equation, $2x^{2} – 6x + 3$ = 0.

x=$\dfrac{-b\pm\sqrt{b^{2}-4ac}}{2a}$

= $\dfrac{(-(-6) ± \sqrt{(-62-4(2)(3)) )}}{ 2(2)}$

=$ \dfrac{(6±2\sqrt{3} )}{4}$

=$\dfrac{(3±\sqrt{3})}{2}$

Therefore, the roots for the given equation are $\dfrac{(3+\sqrt{3})}{2}$and $\dfrac{(3-\sqrt{3})}{2}$

Additional Questions

Find the values of k for each of the following quadratic equations so that they have two equal roots.
(i) $2x^{2} + kx$ + 3 = 0

(ii) kx (x – 2) + 6 = 0

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Is the following situation possible? If so, determine their present ages. The sum of the ages of the two friends is 20 years. Four years ago, the product of their age in years was 48.

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Is it possible to design a rectangular park with a perimeter of 80 and an area of 400 $ m^{2}$ ? If so, find its length and breadth.

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Find the nature of the roots of the following quadratic equations. If the real roots exist, find them:
(i) $2x^{2} – 3x + 5$ = 0

(ii) $3x^{2} – 4\sqrt{3}x + 4$ = 0

(iii) $2x^{2} – 6x + 3$ = 0

Answer

Find the values of k for each of the following quadratic equations so that they have two equal roots.
(i) $2x^{2} + kx$ + 3 = 0

(ii) kx (x – 2) + 6 = 0

Answer

Is it possible to design a rectangular mango grove whose length is twice its breadth and the area is 800 $m^{2}$? If so, find its length and breadth.

Answer

Is the following situation possible? If so, determine their present ages. The sum of the ages of the two friends is 20 years. Four years ago, the product of their age in years was 48.

Answer

Is it possible to design a rectangular park with a perimeter of 80 and an area of 400 $ m^{2}$ ? If so, find its length and breadth.

Answer
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