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0 votes
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in Quadratic Equations by (34.1k points)
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Which of the following equations is quadratic 

i. x2 + 2x + 11 = 0 

ii. x2 – 2x + 5 = x2 

iii. (x + 2)2 = 2x2

2 Answers

+1 vote
by (33.5k points)
selected by
 
Best answer

i. The given equation is

x2 + 2x + 11 = 0

Here, x is the only variable and maximum index of the variable is 2.

a = 1, b = 2, c = 11 are real numbers and a ≠ 0.

The given equation is a quadratic equation.

ii. The given equation is

x2 – 2x + 5 = x2 

∴ x2 – x2 + 2x – 5 = 0 

∴ 2x – 5 = 0

Here, x is the only variable and maximum index of the variable is not 2.

∴ The given equation is not a quadratic equation.

iii. The given equation is

(x + 2)2 = 2x2 

∴ x2 + 4x + 4 = 2x2 

∴ 2x2 – x2 – 4x – 4 = 0 

∴ x2 – 4x – 4 = 0

Here, x is the only variable and maximum index of the variable is 2.

a = 1, b = -4, c = —4 are real numbers and a ≠ 0.

∴ The given equation is a quadratic equation.

+1 vote
by (210 points)


Except (ii) both are quadratic equation 

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