If a-b=10,a+c=20, and b-c=-30 then find a
a. 4
b. 2
c. 1
d. 0
ALGEBRA QUESTION?
2018-02-20 7:53 pm
回答 (11)
2018-02-20 10:04 pm
✔ 最佳答案
b-c=-30c=b+30
a-b=10
a=10+b
a+c=20
10+b +b +30=20
2b+40=20
2b=-20
b=-10
c=b+30
c=-10+30
c=20
a=10+b
a=10-10
a=0
2018-02-20 8:51 pm
a - b = 10 …… [1]
a + c = 20 …… [2]
b - c = -30 …… [3]
[1] + [2] + [3] :
a - b + a + c + b - c = 0
2a = 0
a = 0
The answer: d. 0
a + c = 20 …… [2]
b - c = -30 …… [3]
[1] + [2] + [3] :
a - b + a + c + b - c = 0
2a = 0
a = 0
The answer: d. 0
2018-02-21 1:04 pm
If a - b = 10,,a + c = 20,and b - c = -30 then find a
a - c = -20,
a = 0
Answer choice:
d. 0
a - c = -20,
a = 0
Answer choice:
d. 0
2018-02-20 11:59 pm
(1) : a - b = 10
(2) : a + c = 20
(3) : b - c = - 30
You calculate (1) - (2)
(a - b) - (a + c) = 10 - 20
a - b - a - c = - 10
b + c = 10 → recall (3): b - c = - 30 → b = c - 30
c - 30 + c = 10
2c = 40
→ c = 20
Recall (3): b - c = - 30
b = c - 30 → recall: c = 20
b = 20 - 30
→ b = - 10
Recall (1) : a - b = 10
a = b + 10 → recall: b = - 10
a = - 10 + 10
→ a = 0
(2) : a + c = 20
(3) : b - c = - 30
You calculate (1) - (2)
(a - b) - (a + c) = 10 - 20
a - b - a - c = - 10
b + c = 10 → recall (3): b - c = - 30 → b = c - 30
c - 30 + c = 10
2c = 40
→ c = 20
Recall (3): b - c = - 30
b = c - 30 → recall: c = 20
b = 20 - 30
→ b = - 10
Recall (1) : a - b = 10
a = b + 10 → recall: b = - 10
a = - 10 + 10
→ a = 0
2018-02-20 11:55 pm
If a - b = 10, a + c = 20, and b - c = -30 then find a.
b + c = 10, b = -10
Answer choice:
d. 0
b + c = 10, b = -10
Answer choice:
d. 0
2018-02-20 11:20 pm
Add the first and third equations and you get a - c = -20. Add this with the second equation and you get 2a = 0, which makes a = 0. D).
2018-02-20 8:22 pm
a - b = 10,................(1)
a + c = 20, ................(2)
b - c = -30..................(3)
Add (1) and (3)
a - c = -20 ................(4)
Add (2) and (4)
2a = 0
a = 0 ..............[ b = -10, c = 20 ]
a + c = 20, ................(2)
b - c = -30..................(3)
Add (1) and (3)
a - c = -20 ................(4)
Add (2) and (4)
2a = 0
a = 0 ..............[ b = -10, c = 20 ]
2018-02-20 8:04 pm
a–b=10
a+c=20
b–c=–30
–a+b = –10
a+c = 20
add
b+c = 10
b–c = –30
add these two
2b = –20
b = –10
substitute
a–b = 10
a–( –10) = 10
a+10 = 10
a = 0 ⬅
a–b = 10
–b = 10
b = –10 ⬅
b+c = 10
–10 + c = 10
c = 20 ⬅
check
a–b=10
0+10 = 10 ok
a+c=20
0+20=20 ok
b–c=–30
–10–20 = –30 ok
a+c=20
b–c=–30
–a+b = –10
a+c = 20
add
b+c = 10
b–c = –30
add these two
2b = –20
b = –10
substitute
a–b = 10
a–( –10) = 10
a+10 = 10
a = 0 ⬅
a–b = 10
–b = 10
b = –10 ⬅
b+c = 10
–10 + c = 10
c = 20 ⬅
check
a–b=10
0+10 = 10 ok
a+c=20
0+20=20 ok
b–c=–30
–10–20 = –30 ok
2018-02-20 7:54 pm
1
2018-02-20 9:05 pm
a - b = 10
a + ( b + 30 ) = 20
a - b = 10
a + b = - 10________add
2a = 0
a = 0
b = - 10
c = 20
a + ( b + 30 ) = 20
a - b = 10
a + b = - 10________add
2a = 0
a = 0
b = - 10
c = 20
2018-02-20 9:05 pm
a-b=10 ----(1)
a+c =20 ----(2)
subtract (2) from (1)
-b-c = -10
multiply both sides by -1
b+c = 10
b-c = -30
add:
2b = -20
b=-10
a-b=10 -----(1)
a-(-10) = 10
a+10=10
a=0
a+c =20 ----(2)
subtract (2) from (1)
-b-c = -10
multiply both sides by -1
b+c = 10
b-c = -30
add:
2b = -20
b=-10
a-b=10 -----(1)
a-(-10) = 10
a+10=10
a=0
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