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MariettaO [177]
3 years ago
5

Solve the system of equations using the substitution method.

Mathematics
1 answer:
Karolina [17]3 years ago
3 0
Substitution is where we first Isolate one of the unknowns, express it in terms of the other unknown, and replace the isolated unknown with the other unknown in another equation. So that each time we only need to deal with one unknown. I think you'll get a better idea here:

First name these 2 equations with 1 and 2.
4x + 5y = 7 (1)
y = 3x + 9 (2)

Since y is already isolated in (2), so we can skip the isolation step and continue to substitute.

Substitute (2) into (1).
4x + 5(3x+9) = 7

Expand.
4x + 15x + 45 = 7

Group.
19x + 45 = 7

Shift +45 to the other side and turn it into -45.

19x = 7 - 45
19x = -38

Shift x19 to the other side, turn it into /19.
X = - 38/19
X = - 2

Now we solved x already, we can just substitute x= - 2 back to equation (2).

y = 3(-2) + 9
y = - 6 + 9
y = 3

So, the answers are
x = - 2
y = 3
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Step-by-step explanation:

because in -4-2 the -4 is still a negative 4 and in (-4)-2 the (-4) is still negative 4 so either way the answer will be the same

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9) Let<br> X-2, x, x+3 <br> be the first 3 terms of a geometric sequence. FInd the value of x..
Reil [10]
Hello,

Let's r the ration

We suppose x ≠0

x=r*(x-2)==>r=x/(x-2)

x+3=r*x==> (x+3)/x=x/(x-2)==>(x+3)(x-2)=x²
==>x²+3x-2x-6=x² ==>x-6=0==>x=6

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7 0
3 years ago
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Devaughn is 15 years younger than Sydney. The sum of their ages is 37 . What is Sydney's age?
posledela
Hi,
Let Sydney's age be x.
Devaughn=(x-15)
x+(x-15)=37
x+x-15=37
2x-15=37
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2x=52
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Sydney is 26 years old.
Hope this Helps you.
7 0
3 years ago
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