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Quadratic Equations Test - 19

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Quadratic Equations Test - 19
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  • Question 1
    1 / -0
    Is the following equation quadratic?
    $$(x\, +\, 3) (x\, -\, 4)\, =\, 0$$
    Solution
    $$Answer=1$$
    The equation $$(x\, +\, 3) (x\, -\, 4)\, =\, 0$$ can be formed as
    $$x^2 - x -12 =0 $$ has the highest power as 2. Thus, it is quadratic equation.
  • Question 2
    1 / -0
    The mentioned equation is in which form?
    $$\dfrac{q^{2}- 4}{q^{2}}\, =\, -3$$
    Solution
    Given equation is $$\dfrac{q^2 - 4}{q^2} = -3$$
    $$\Rightarrow q^2 - 4 = -3q^2$$
    $$\Rightarrow 4q^2 = 4$$
    $$\Rightarrow q^2 = 1$$
    The highest power of $$q$$ is $$2$$. Hence, it is a quadratic equation.
  • Question 3
    1 / -0
    The mentioned equation is in which form?
    $$3y^{2}\,-\, 7\, =\, \sqrt{3}\,y$$
    Solution
    The highest power of y is 2. Hence, the equation is quadratic.
  • Question 4
    1 / -0
    Is the following equation quadratic?
    $$\displaystyle -\frac{5}{3}\, x^{2}\, =\, 2x\, +\, 9$$
    Solution
    $$Answer=1$$
    The equation, $$\displaystyle -\frac{5}{3}\, x^{2}\, =\, 2x\, +\, 9$$ has the highest power as 2. 
    Thus, the equation is quadratic.
  • Question 5
    1 / -0
    Is the following equation quadratic?
    $$13\, =\, -5y^{2}\, -\, y^{3}$$
    Solution
    Answer=0
    The equation $$13 = -5y^2 - y^3$$ has the highest power as 3. Thus, it is not quadratic equation.
  • Question 6
    1 / -0
    Find discriminant of $$5x^2+2x+1=0$$
    Solution
    The discriminant $$D={ b }^{ 2 }- 4ac = 4 - 4(5)(1) = -16$$
  • Question 7
    1 / -0
    Find a quadratic equation, from the equations given below, having same discriminant as $$5x^2+2x+1=0$$
    Solution
    Given: set of quadratic equations
    To find: the equation having same discriminant as $$5x^2+2x+1=0$$
    Sol: The equation $$5x^2+2x+1=0$$ is of form $$ax^2+bx+c=0$$
    $$\therefore a=5, b=2, c=1$$
    The discriminant of this equation becomes 
    $$b^2-4ac=2^2-4(5)(1)=4-20=-16$$
    (i) $$-x^2+4x-8$$ this is also of the form $$ax^2+bx+c$$
    $$\therefore a=-1, b=4, c=-8$$
    The discriminant of this equation becomes 
    $$b^2-4ac=4^2-4(-1)(-8)=16-32=-16$$
    (ii) $$x^2+3x-7$$ this is also of the form $$ax^2+bx+c$$
    $$\therefore a=1, b=3, c=-7$$
    The discriminant of this equation becomes 
    $$b^2-4ac=3^2-4(1)(-7)=9+28=37$$
    (iii) $$4x^2-5\implies 4x^2-0x-5$$ this is also of the form $$ax^2+bx+c$$
    $$\therefore a=4, b=0, c=-5$$
    The discriminant of this equation becomes 
    $$b^2-4ac=0^2-4(4)(-5)=0+80=80$$
    (iv) $$-2x^2-3x+6$$ this is also of the form $$ax^2+bx+c$$
    $$\therefore a=-2, b=-3, c=6$$
    The discriminant of this equation becomes 
    $$b^2-4ac=(-3)^2-4(-2)(6)=9+48=57$$
  • Question 8
    1 / -0
    Find the roots of the quadratic equation by applying the quadratic formula$$\displaystyle 2x^2 - 7x + 3 = 0$$
    Solution
    Given equation is $$2x^{2}-7x+3=0$$
    Hence, $$a=2,b=-7,c=3$$
    Therefore, $$x=\dfrac{-b\pm\sqrt{b^{2}-4ac}}{2a}$$
    $$=\dfrac{7\pm\sqrt{25}}{4}$$
    $$=\dfrac{7\pm5}{4}$$
    Thus, $$x=3$$ and $$x=\dfrac{1}{2}$$
  • Question 9
    1 / -0
    Is the following equation a quadratic equation?
    $$\displaystyle 3x + \frac{1}{x} - 8 = 0$$
    Solution
    Given, $$3x + \dfrac{1}{x} - 8 = 0$$
    $$\Rightarrow \dfrac{3x^2+1-8x}{x}=0$$
    $$\Rightarrow 3x^2+1-8x=0$$
    Comparing  it with the standard form of quadratic equation $$x^2+bx+c=0, a\neq 0$$
    Here, $$a=3$$
    Thus, it is a quadratic equation.
  • Question 10
    1 / -0
    Is the following equation a quadratic equation?
    $$(x + 2)^3 = x^3 - 4$$
    Solution
    Given equation is $$(x + 2)^3 = x^3 - 4$$
    $$\rightarrow x^3+2^3+3\times x\times 2(x+2)=x^3-4$$
    $$\Rightarrow x^3+8+6x(x+2)=x^3-4$$
    $$\Rightarrow x^3+8+6x^2+12x-x^3+4=0$$
    $$\Rightarrow 6x^2+12x+12=0$$
    Comparing it with the standard form of quadratic equation $$x^2+bx+c=0, a\neq 0$$.
    Here, $$a=6$$
    Thus, it is a quadratic equation.
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