SOLUTION: Given that a - b = 10 and 2 (a^2 - b^2) = 640 .find the value of a + b

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Question 983422: Given that a - b = 10 and 2 (a^2 - b^2) = 640 .find the value of a + b

Found 2 solutions by Fombitz, Cromlix:
Answer by Fombitz(32388) About Me  (Show Source):
Answer by Cromlix(4381) About Me  (Show Source):
You can put this solution on YOUR website!
Hi there,
a - b = 10
so a = b + 10
2(a^2 - b^2) = 640
Multiply out
2a^2 - 2b^2 = 640
Substitute for 'a' (b + 10)
2(b + 10)^2 - 2b^2 = 640
Expand
2(b^2 + 20b + 100) - 2b^2 = 640
2b^2 + 40b + 200 - 2b^2 = 640
Collect like terms
2b^2 - 2b^2 + 40b = 640 - 200
40b = 440
b = 11
Substitute b = 11 into
a - b = 10
a - 11 = 10
a = 10 + 11
a = 21
Therefore:
a + b = 21 + 11 = 32
Hope this helps:-)