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5 votes
If the sum as well as the product of roots of a quadratic equation is 9, then the equation is:

a)
x^(2) +9x-18 = 0
b)
x^(2) -18x+9=0
c)
x^(2) +9x+9=0
d)
x^2 -9x +9 = 0

Give a detailed answer

asked
User MBN
by
8.6k points

2 Answers

4 votes


x_1+x_2=x_1x_2=9

From Vieta's formulas we have


x_1+x_2=-(b)/(a)\\x_1x_2=(c)/(a)

Therefore


-(b)/(a)=9\\(c)/(a)=9\\

It's not possible to find the exact values of
a,b and
c based only on these two equations.

However, if we look at possible answers, we can notice, that in each one
a=1.

Therefore


-b=9\Rightarrow b=-9\\c=9

Substituting those values into the general quadratic formula, we get


y=x^2-9x+9

answered
User Mitch Goudy
by
8.6k points
3 votes


\implies Question:-

If the sum as well as the product of roots of a quadratic equation is 9, then the equation is:

a)
x^(2) +9x-18 = 0

b)
x^(2) -18x+9=0

c)
x^(2) +9x+9=0

d)
x^2 -9x +9 = 0


\implies Answer:-

d)
x^2 -9x +9 = 0


\implies Explanation:-

Given:-

  • Sum of zeros ( α + ß ) = 9
  • Product of zeros ( αß ) = 9

According to the Quadratic formula:-


\longrightarrow {x}^(2) - ( \alpha + \beta )x + \alpha \beta

Substituting the values,


\longrightarrow {x}^(2) - 9x + 9 \\

So the correct answer is ,


\longrightarrow {x}^(2) - 9x + 9 \\

_______________XxAuroraxX<3_______

answered
User Alexandernst
by
8.2k points

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