For which values of the parameter "p" the equation
"8x^2 - 4x + 1 - p = 0" (with unknown x) has two different real roots less than 1?

Can you please explain in detail how this problem is solved?

Respuesta :

Answer:

[tex]\dfrac12 < p < 5[/tex]

Step-by-step explanation:

To solve this, we need to use the discriminant.

Discriminant

[tex]b^2-4ac\quad\textsf{when}\:ax^2+bx+c=0[/tex]

[tex]\textsf{when }\:b^2-4ac > 0 \implies \textsf{two real roots}[/tex]

[tex]\textsf{when }\:b^2-4ac=0 \implies \textsf{one real root}[/tex]

[tex]\textsf{when }\:b^2-4ac < 0 \implies \textsf{no real roots}[/tex]

If the given equation has 2 real roots, then we need to use:

[tex]b^2-4ac > 0[/tex]

Given equation:  [tex]8x^2-4x+1-p=0[/tex]

[tex]\implies a=8, \quad b=-4, \quad c=(1-p)[/tex]

Substituting these values into [tex]b^2-4ac > 0[/tex] and solve for p:

[tex]\implies (-4)^2-4(8)(1-p) > 0[/tex]

[tex]\implies 16-32(1-p) > 0[/tex]

[tex]\implies 16-32+32p > 0[/tex]

[tex]\implies -16+32p > 0[/tex]

[tex]\implies 32p > 16[/tex]

[tex]\implies p > \dfrac{16}{32}[/tex]

[tex]\implies p > \dfrac12[/tex]

For the roots to be less than 1, first find the value of p when the root is 1.

If the root is 1, then [tex](x-1)[/tex] will be a factor, so [tex]f(1)=0[/tex]

Substitute [tex]x=1[/tex] into the given equation and solve for p:

[tex]\implies 8(1)^2-4(1)+1-p=0[/tex]

[tex]\implies 5-p=0[/tex]

[tex]\implies p=5[/tex]

Therefore, the values of p for which the given equation has two different real roots less than 1 are:

[tex]\dfrac12 < p < 5[/tex]