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Answers:
- System 1: x = 3 and y = -5
- System 2: x = 1 and y = 2
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Explanation:
For now, let's focus on system 1.
We have identical copies of "2y" in each equation, which means that if we were to subtract the equations straight down, then the y terms cancel out. That allows us to solve for x.
- The x terms subtract to 7x-x = 6x
- The y terms subtract to 0 and go away
- The right hand sides subtract to 11 minus (-7) = 11-(-7) = 11+7 = 18
After doing those subtractions, we have the new equation 6x = 18 which solves to x = 3. Divide both sides by 6 to isolate x.
Once we know x, we can find out y.
7x+2y = 11
7(3)+2y = 11
21+2y = 11
2y = 11-21
2y = -10
y = -10/2
y = -5
or we can say
x+2y = -7
3+2y = -7
2y = -7-3
2y = -10
y = -10/2
y = -5
We should lead to the same y value either way. This helps confirm we have the correct x value.
Overall, the solution to system 1 is (x,y) = (3, -5)
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Now onto system 2.
Unfortunately, we don't have identical y terms this time. But what we can do is double everything in the second equation to go from -x+y = 1 to -2x+2y = 2.
The new equivalent system is
Now we have the same situation as before: Subtract straight down, solve for x.
- The x terms subtract to 7x-(-2x) = 7x+2x = 9x
- The y terms go away when subtracting
- The right hand sides subtract to 11-2 = 9
So we have 9x = 9 and that solves to x = 1.
We'll use this x to find the y value.
7x+2y = 11
7(1)+2y = 11
7+2y = 11
2y = 11-7
2y = 4
y = 4/2
y = 2
Or you could pick on the second equation
-x+y = 1
-1+y = 1
y = 1+1
y = 2
<h2>Answer and Explanation to questions 13,14,15</h2>
13) as given in the question.
14) Since Y is the midpoint of XZ. So, Y will divide XZ in equal halves into XY and YZ.
15)
and
. So,
∠3 is supplementary to ∠1 means: ∠3 + ∠1 = 180°
And, according to figure ∠1 + ∠2 = 180° as ∠1 and ∠2 form a straight line.
∠3 + ∠1 = 180° .............(i)
∠1 + ∠2 = 180° .............(ii)
subtracting equation (i) and (ii) will give ∠3 = ∠2 ..........(iii)
15) ∠3 is supplementary to ∠1 as given in the question
16) ∠2 is supplementary to ∠1 as shown be equation (ii)
18) ∠3 ≅ ∠2 as shown by equation (iii)
<h2>Answer and Explanation to questions 19</h2>∠3 and ∠4 form a straight line. Therefore, ∠3 + ∠4 = 180° .......(i)
∠4 and ∠5 form a straight line. Therefore, ∠4 + ∠5 = 180° .......(ii)
subtracting equation (i) and (ii)
∠3 + ∠4 - (∠4 + ∠5) = 180°-(180°)
∠3 + ∠4 - ∠4 - ∠5 = 180°-180°
∠3 - ∠5 = 0
∴ ∠3 = ∠5 (Hence Proved)