Solve the equation x^3-13x^2+47x-35=0 given that 1 is a zero of f(x)= x^3-13x^2+47x-35.


The solution set is_______



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Answer: x = {1 , 5 , 7}

Step-by-step explanation:

We have x^3 - 13x^2 + 47x - 35 = 0.

Taking -13x^2, we can split it up into -x^2 - 12x^2

Taking 47x, we can split it up into 12x + 35x

Putting these into the original equation, we have:

x^3 - x^2 - 12x^2 + 12x + 35x - 35 = 0

From this you can see that we have 3 pairs of terms that we can easily factor. From the first pair we can factor x^2, from the second we can factor -12x, and from the third one we can factor 35.

1. (x^3 - x^2)  = x^2 (x - 1)

2. (- 12x^2 + 12x) = -12x (x - 1)

3. (35x - 35) = 35 (x - 1)

Putting them back into the equation we have:

x^2 (x - 1) - 12x (x - 1) + 35 (x - 1) = 0

               (x^2 - 12x + 35) (x - 1) = 0

To find the roots, we can set (x - 1) = 0 and  (x^2 - 12x + 35) = 0.

x - 1 = 0

    x = 1 (First root)

x^2 - 12x + 35 = 0

Factoring using the Sum-Product Rule:

Sum of -12, Product of 35 --> -7 and -5

x^2 - 12x + 35 = 0

  (x - 7) (x - 5) = 0

We can see that x = 7 and x = 5.

So the solution set it x = {1 , 5 , 7}

The solution set will be {1,5,7}

What is zero of a function?

Zero of a function is the root of the function for which the function value of that root will be zero.

If a is the zero of function f(x)=0 then f(a)=0.

So according to question,

the equation is

x³-13x²+47x-35=0

spilting -13x² as -x²-12x² and 47x as 12x+35x

⇒x³-x²-12x²+12x+35x-35=0

⇒x²(x-1)-12x(x-1)+35(x-1)=0

taking (x-1) common from each term

⇒(x-1)(x²-12x+35)=0

In another way, as 1 is zero of x³-13x²+47x-35=0

then (x-1) is one factor of x³-13x²+47x-35=0

another factor will be x³-13x²+47x-35/(x-1)=x²-12x+35

for which we can write the equation x³-13x²+47x-35=(x-1)(x²-12x+35).

⇒(x-1)(x²-5x-7x-35)=0

⇒(x-1)(x(x-5)-7(x-5))=0

⇒(x-1)(x-5)(x-7)=0

⇒x-1=0  or  x-5=0  or  x-7=0

⇒x=1   or   x=5   or   x=7

Therefore The solution set will be {1,5,7}

Learn more about the zero of the function

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