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

Question

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

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Kim Cúc 5 years 2021-09-02T11:23:14+00:00 1 Answers 16 views 0

Answers ( )

  1. thienthanh
    0
    2021-09-02T11:24:26+00:00
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    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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