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The expression x^2- x + 8.75 factors as (x + 2.5)(x - a) for some positive value "a". What is a?
step by step, please.


Sagot :

Answer:

3.5

Step-by-step explanation:

Write out quadratic

[tex] {x}^{2} - x + 8.75[/tex]

We are given that x+2.5 is a factor.

So our roots look like

[tex](x + 2.5)(x - a)[/tex]

Let apply the foil method to find some missing parts.

[tex]x \times x = {x}^{2} [/tex]

[tex]x \times - a = - ax[/tex]

[tex]2.5 \times x = 2.5[/tex]

[tex]2.5 \times - a = - 2.5a[/tex]

We know that the outer terms must multiply to 8.75. We also know that the middle terms must add up to -1.

[tex] - 2.5a = 8.75[/tex]

[tex] 2.5x - ax = -1[/tex]

The only number that satisfy this equation is

[tex] - 3.5[/tex]

Since it already negative, it is

[tex]3.5[/tex]