The product of all the rational roots of the equation (x2−9x+11)2−(x−4)(x−5)=3\left(x^2 - 9x + 11\right)^2 - (x - 4)(x - 5) = 3, is equal to

Answer: 14

Step-by-step solution

Step 1: Simplify the equation

First, we expand the product (x−4)(x−5)(x-4)(x-5). This gives us x2−5x−4x+20x^2 - 5x - 4x + 20, which simplifies to x2−9x+20x^2 - 9x + 20. We substitute this back into the original equation.

Step 2: Introduce a substitution

To simplify the equation further, we observe that the term x2−9xx^2 - 9x appears multiple times. Let y=x2−9x+11y = x^2 - 9x + 11. Then x2−9x+20x^2 - 9x + 20 can be written as (x2−9x+11)+9(x^2 - 9x + 11) + 9, which is y+9y+9. Substituting these into the equation gives us a quadratic equation in terms of yy.

Step 3: Solve for y

Now we solve the quadratic equation for yy. Rearranging the terms, we get y2−y−12=0y^2 - y - 12 = 0. Factoring this quadratic equation, we find (y−4)(y+3)=0(y-4)(y+3)=0. This yields two possible values for yy: y=4y=4 or y=−3y=-3.

Step 4: Substitute back and solve for x

We now substitute the values of yy back into our original substitution y=x2−9x+11y = x^2 - 9x + 11. This gives us two separate quadratic equations for xx. For y=4y=4, we have x2−9x+11=4x^2 - 9x + 11 = 4, which simplifies to x2−9x+7=0x^2 - 9x + 7 = 0. For y=−3y=-3, we have x2−9x+11=−3x^2 - 9x + 11 = -3, which simplifies to x2−9x+14=0x^2 - 9x + 14 = 0.

Step 5: Find rational roots

We solve each quadratic equation for xx. For x2−9x+7=0x^2 - 9x + 7 = 0, the discriminant is D=(−9)2−4(1)(7)=81−28=53D = (-9)^2 - 4(1)(7) = 81 - 28 = 53. Since 5353 is not a perfect square, the roots are irrational. For x2−9x+14=0x^2 - 9x + 14 = 0, we can factor it as (x−2)(x−7)=0(x-2)(x-7)=0, which gives rational roots x=2x=2 and x=7x=7.

Step 6: Calculate the product of rational roots

The rational roots of the original equation are 22 and 77. The product of these rational roots is 2×7=142 \times 7 = 14.

More from this chapter

All Complex Numbers and Quadratic Equations solutions →

Solve your own maths question free →