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vivado [14]
3 years ago
12

A girl is twice as old as her sister. Five years hence, the product of their ages (in years) will be 375. Find their present age

s. A girl is twice as old as her sister. Five years hence, the product of their ages (in years) will be 375. Find their present ages.
Mathematics
1 answer:
Orlov [11]3 years ago
7 0

Answer: girls=20, sister=10

Step-by-step explanation:

Let x = the girl's sister's age (present)

Let 2x= the girl's age (present)

-------------------------------------------------------------

According to the question

(x+5)(2x+5)=375

Expand parentheses by FOIL (First Outer Inner Last)

2x²+5x+10x+25=375

Combine like term (5x and 10x)

2x²+15x+25=375

Subtract 375 on both sides

2x²+15x+25-375=375-375

2x²+15x-350=0

Find the factors (cross factor)

(x-10)(x+17.5)=0

x=10 or x=-17.5 (rej) ⇔ the age can't be negative

the girl's age is 20, and her sister's age is 10.

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3 years ago
Solve this equation for x: 2x^2 + 12x - 7 = 0
zhannawk [14.2K]

Answer:

x=0.5355 or x=-6.5355

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Step-by-step explanation:

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On observation, the trinomial is not factorizable so we use the Completing the square method.

Step 1: Isolate the constant term by adding 7 to both sides

2x^2 + 12x - 7+7 = 0+7\\2x^2 + 12x=7

Step 2: Divide the equation all through by the coefficient of x^2 which is 2.

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Step 3: Divide the coefficient of x by 2, square it and add it to both sides.

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Therefore, we have:

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Step-by-step explanation:

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erica [24]

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