Question 39

Which of the following quadratic equations has real roots?

Solution

A quadratic equation : $$ax^2 + bx + c = 0$$ has real roots iff Discriminant, $$D = b^2 - 4ac \geq 0$$

(A) : $$3x^{2}-5x+2=0$$

=> D = $$(-5)^2 - 4(3)(2) = 25 - 24 = 1$$

(B) : $$3x^{2}-4x+2=0$$

=> D = $$(-4)^2 - 4(3)(2) = 16 - 24 = -8$$

(C) : $$4x^{2}-3x+2=0$$

=> D = $$(-3)^2 - 4(4)(2) = 9 - 32 = -23$$

(D) : $$5x^{2}-2x+2=0$$

=> D = $$(-2)^2 - 4(5)(2) = 4 - 40 = -36$$

Thus, the equation : $$3x^{2}-5x+2=0$$ has real roots.


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