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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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Her original amount of money can be represented by the variable x

Because we are spending one-fourth of her money, and “of” translate to multiply, we can write 1/4(x), or equivalently we can say 0.25x of her money, if you prefer decimal.

When you say 1/2 of it, this refers to the original amount of money, x, unless the problem wants you to figure how much 1/2 of the remaining amount is. So if the problem is directly asking for 1/2 of it, that would’ve half of x, or 0.5x in decimal.

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Combine like terms on the left, and we have 0.25x=0.50.

Divide by 0.25 on both sides.

We have x equals 2.

So she started with $2. To check this, we ask ourselves does having $2, and spending 1/4 of it and spending 1/2 of it, then result to 50 pence?

Yes it does, because 2–1–0.5 does in fact equal 0.50 (50pence)

Su cantidad original de dinero puede ser representada por la variable x Debido a que estamos gastando una cuarta parte de su dinero, y "de" se traduce para multiplicar, podemos escribir 1/4 (x), o equivalentemente podemos decir 0.25x de su dinero , si lo prefiere decimal. Cuando dices la mitad, esto se refiere a la cantidad original de dinero, x, a menos que el problema quiera que calcules la mitad de la cantidad restante. Entonces, si el problema es pedir directamente la mitad, tendría la mitad de x, o 0.5x en decimal. El restante era 50 centavos, por lo que la cantidad original menos 1/4 de la cantidad menos la mitad de la cantidad es igual a 50 peniques o .50, lo que nos da la ecuación: x-0.25x-0.5x = .50 Combina términos semejantes a la izquierda, y tenemos 0.25x = 0.50 Divide por 0.25 en ambos lados, tenemos x igual a 2. ella empezó con 2 dólares. Para comprobar esto, nos preguntamos si tener 2 dólares y gastar 1/4 de ellos y gastar la mitad de ellos, ¿da como resultado 50 centavos? sí eso

Step-by-step explanation:

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