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Marina CMI [18]
3 years ago
11

5r^2-38r-16 i must factor by grouping but im very lost

Mathematics
1 answer:
scoray [572]3 years ago
7 0
So let's take this step by step. The only two numbers that will give you 5 is 1 and 5. The numbers that can give you 16 is 1, 2, 4, 8, 16. The whole idea behind factoring is playing with these numbers and seeing what gives you -38. 

Let's set up the factors now: 

(5r + __) (r - __) 

What two numbers could you put in the blanks? If you multiply everything together, you'll have to get 5r^2-38r-16. 

If you play around with the numbers, 2 and 8 could be used. So let's plug them in.

(5r + 2)(r - 8) 

If you multiply them out, you'll get 5r^2 - 40r + 2r - 16, or 5r^2 - 38r -16. Hope that helps. 
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Step-by-step explanation:

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Does the equation 2x-7=5+x have exactly one solution
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4 0
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Let x1 = 12, y1 = 15, and y2 = 3. Let y vary inversely with x. Find x2.
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We have that an inverse variation in a function is given by:
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 We must find the value of the constant k.
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x2 = 60
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3 years ago
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