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Find the zeroes of the quadratic polynomial (8x^2 – 4) and verify the relation between the zeroes and the coefficients.

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Questions

Find the zeroes of the quadratic polynomial (8x2 – 4) and verify the relation between the zeroes and the coefficients.

Find the zeros of the following quadratic polynomial and verify the relationship between the zeros and the coefficients:

8x2 – 4

Sum
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Solution

We have: 

f(x) = 8x2 – 4 

It can be written as 8x2 + 0x – 4 

= `4{(sqrt(2)x)^2 - (1)^2}` 

= `4(sqrt(2)x + 1) (sqrt(2)x - 1)` 

∴ f(x) = 0 ⇒ `(sqrt(2)x + 1) (sqrt(2)x - 1) = 0` 

⇒ `(sqrt(2)x + 1) = 0` or `sqrt(2)x - 1 = 0` 

⇒ `x = (-1)/sqrt(2)` or `x = 1/sqrt(2)` 

So, the zeroes of f(x) are `(-1)/sqrt(2)` and `1/sqrt(2)` 

Here the coefficient of x is 0 and the coefficient of x2 is `sqrt(2)` 

Sum of zeroes = `(-1)/sqrt(2) + 1/sqrt(2)`

= `(-1 + 1)/sqrt(2)`

= `0/sqrt(2)`

= `(-("Coefficent of"  x))/(("Coefficient of"  x^2))` 

Product of zeroes = `(-1)/sqrt(2) xx 1/sqrt(2)`

= `(-1 xx 4)/(2 xx 4)`

= `(-4)/8`

= `("Constant term")/(("Coefficient of"  x^2))`

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Chapter 2: Polynomials - EXERCISE 2A [Page 52]

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R.S. Aggarwal Mathematics [English] Class 10
Chapter 2 Polynomials
EXERCISE 2A | Q 12. | Page 52

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