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3 years ago

Slove x^2-8x=20 by completing the square. which is the solution set of equation?

Mathematics

1 answer:

sveticcg [70]3 years ago

3 0

x^2-8x=20

Move +20 to the other side. Sign changes from +20 to -20

x^2-8x-20=20-20

x^2-8x-20=0

Think about two numbers that equals to -20 and -8.

(x-10)(x+2)=0

x-10=0 ( move -10 to the other side). Sign changes from -10 to 10

x-10+10=0+10

x=10

x+2=0 ( move +2 to the other side). Sign changes from +2 to -2

x+2-2=0-2

x=-2

Answer:

x=10, x=-2

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Shauna spent $175 on a pair of shoes.She spent 1/9 of the remaining money on a shirt.If he still had 4/7of his moneyleft,how muc

KIM [24]

Answer:

$490

Step-by-step explanation:

Shauna spent $175 on a pair of shoes.

She spent 1/9 of the remaining money on a shirt.

If he still had 4/7 of his money left,how much did he have at first ?

Solution:

Let at first, Shauna have = $x$

Money spent on a pair of shoes = $175

Remaining money = $x-175$

<u>As she spent 1/9 of the remaining money on a shirt.</u>

Money spent on shirt = $\frac{1}{9} \times(x-175)=\frac{x}{9} -\frac{175}{9}$

As he still had $\frac{4}{7}$ of his money left:-

Money left = $\frac{4}{7}\ of\ his\ money=\frac{4x}{7}$

Money left with Shauna = Total money, she had at first -(Money spent on a pair of shoes + Money spent on shirt )

$\frac{4x}{7} =x-(175+{\frac{x}{9} -\frac{175}{9} )\\\\\\$

$\frac{4x}{7} =x-(\frac{175}{1} -\frac{175}{9} +\frac{x}{9} )\\\\ \frac{4x}{7} =x-(\frac{1575-175}{9} +\frac{x}{9} )\\\\ \frac{4x}{7}=x-(\frac{1400}{9} +\frac{x}{9} )\\ \\ \frac{4x}{7}=x-\frac{1400}{9} -\frac{x}{9}$

Subtracting both sides by $x$ and adding both sides by $\frac{x}{9}$

$\frac{4x}{7} -x+\frac{x}{9} =-\frac{1400}{9} -x+\frac{x}{9} +x-\frac{x}{9}$

Taking LCM of 7 and 9, we get 63

$\frac{36x-63x+7x}{63} =-\frac{1400}{9} \\ \\ -\frac{20x}{63}=-\frac{1400}{9}$

Adding both side by -

$\frac{36x-63x+7x}{63} =-\frac{1400}{9} \\ \\ \frac{20x}{63}=\frac{1400}{9}$

By cross multiplication:

$20x\times9=1400\times63\\180x=88200\\$

Dividing both sides by 180

$x=490$

Therefore, total $490, she had at first.

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Slove x^2-8x=20 by completing the square. which is the solution set of equation?​

Slove x^2-8x=20 by completing the square. which is the solution set of equation?