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horrorfan [7]
3 years ago
15

Peter is x years old and his sister is 5 years older. If the product of their ages is 84, form an equation in x and solve it to

find peter's age
Mathematics
1 answer:
daser333 [38]3 years ago
3 0

Answer:

x^2 + 5x - 84 = 0

x = 7

Step-by-step explanation:

let the sister's age = y

sister's age (y)  = 5 + x  equation 1

xy = 84  equation 2

Make y the subject of the formula in equation 2

y = 84/x

equate equation 1 and 2

84/x = 5 + x  equation 3

Multiply equation 3 by x

84 = 5x + x^2

x^2 + 5x - 84 = 0

tjis can be solved using quadratic equation

x^2 -7x + 12x -84 = 0

x(x + 12) -7(x + 12)

x = 7 or - 12

age cant be negative so his age is 7

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2 years ago
8х + 5у = -7<br> — 7х + бу = — 4
Levart [38]

Answer: x = -0.2651 and y = -0.9759

Step-by-step explanation:

Solution by substitution method

8x+5y= -7

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Suppose,

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Taking equation (1), we have

8x+5y= -7

⇒8x= -5y -7

⇒x= -5y-7 / 8 →(3)

Putting x= -5y-7 / 8

in equation (2), we get 7x-6y=4

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Now, Putting y= -0.9759 in equation (3), we get

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7 0
3 years ago
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2 years ago
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Step-by-step explanation:

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8 0
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