Question

How to find the missing values ?! I never did this.

Answer 1

Answer:

  (a, b, c) = (2, -6, 2)  or  (2, 2, -6)

Step-by-step explanation:

Expand the expression on the right and match coefficients, or factor the expression on the left and match factors.

  2x³ -8x² -24x = ax(x +b)(x +c)

  2x(x² -4x -12) = ax(x +b)(x +c)

  2x(x -6)(x +2) = ax(x +b)(x +c)

In this form, we can match the numbers to get ...

• a = 2
• b = -6
• c = 2

You may recognize that b and c can be interchanged.

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Alternate solution

If you expand the expression on the right, you get ...

  = ax³ +a(b+c)x² +abcx

This gives you 3 equations:

• a = 2
• 2(b +c) = -8
• 2bc = -24

This is basically the same factoring problem in another form. You have ...

  bc = -12

  b+c = -4

The factors of -12 are ...

  -12 = 1(-12) = 2(-6) = 3(-4) . . . . . . with sums -11, -4, -1

So, b and c are -6 and 2, in no particular order.

  (a, b, c) = (2, -6, 2)  or  (2, 2, -6)