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4 years ago

Solve this system algebraically.

1 answer:

4 0

From y-2x+3=0 we have y=2x-3
So we can replace y by 2x-3 in the equation: 9x+2y=5
And we have 9x+2(2x-3)=5
Or 9x+4x-6=5
and 13x=5+6
Or x=11/13, then y=2x-3= 2. 11/13-3=22/13-3= -17/13

So we have the answer <span>{(11/13, -17/13)}</span>

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If 90 is 80% of a value, what is that value?

Anna71 [15]

So 90 is 4/5 of a number.

4/5n=90

4n=450

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n=112.5

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4 years ago

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viva [34]

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3 years ago

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A meal costs $30 before tax and tip.

Vlad1618 [11]

Answer:

$38.1

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Tax: 30*0.07 = 2.1

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3 years ago

How to solve y=-4x step by step

snow_lady [41]

Answer:

Step-by-step explanation

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3 years ago

If log2 5 = a, log2 3 = b and log2 7 = c, determine an expression for log2 (25/21) in terms of a, b, and c

Ilia_Sergeevich [38]

Answer:

$2a - b -c$

Step-by-step explanation: We know that:

$log_{2} 5 = a\\log_{2} 3 = b\\log_2 7 = c\\$

and we want:

$log_2 \frac{25}{21}$ .

We can form the numerator using just the first fact (since 5^2 is 25) and the denominator using the latter two (since 3*7 = 21).

$log_2 \frac{25}{21} = log_2 \frac{5^2}{3*7}.$

The logarithm of a division can be expanded by subtracting the numerator and denominator (while still keeping the log). The logarithm of a product can be expanded by adding the terms while keeping the log. If the logarithm is raised to a power, we can bring it down as a factor:

$log_2 \frac{5^2}{3*7} = log_2(5)^2 - log_2 (3*7) = 2 log_2(5) - (log_2 3 + log_2 7)$

$= 2 log_2(5) - log_2 3 - log_2 7$ .

Substituting the variables:

$2 log_2(5) - log_2 3 - log_2 7 = 2a - b - c$

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3 years ago