Question

Factor 2x2+25x+50. Rewrite the trinomial with the x-term expanded, using the two factors.

Answer 1

9514 1404 393

Answer:

• rewrite: 2x^2 +5x +20x +50
• factored: (x +10)(2x +5)

Step-by-step explanation:

I find this approach the most straightforward of the various ways that trinomial factoring is explained or diagramed.

You want two factors of "ac" that have a total of "b". Here, that means you want factors of 2·50 = 100 that have a total of 25. It is helpful to know your times tables.

  100 = 1·100 = 2·50 = 4·25 = 5·20 = 10·10

The sums of these factor pairs are 101, 52, 29, 25, and 20. We want the pair with a sum of 25, so that's 5 and 20.

The trinomial can be rewritten using these factors as ...

  2x^2 +5x +20x +50

Then it can be factored by grouping consecutive pairs:

  (2x^2 +5x) +(20x +50) = x(2x +5) +10(2x +5) = (x +10)(2x +5)

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Additional comment

It doesn't matter which of the factors of the pair you write first. If our rewrite were ...

  2x^2 +20x +5x +50

Then the grouping and factoring would be (2x^2 +20x) +(5x +50)

  = 2x(x +10) +5(x +10) = (2x +5)(x +10) . . . . . same factoring