If a+b=7 and ab=12 then a^4-b^4=?
Answers
Answered by
1
Answer:
175 or -175
Find the attachement below, I showed my working out
Attachments:
Answered by
2
Answer:
+175 or -175
Step-by-step explanation:
a + b = 7
b = (7 - a)
ab = 12
a*(7 - a) = 12 [Substituting b = (7-a) ]
7a - a^2 = 12
a^2 - 7a + 12 = 0
a^2 - 4a - 3a + 12 = 0
a(a - 4) - 3(a - 4) = 0
(a - 4)(a - 3) = 0
Therefore, we get a = 4 and a = 3 as solutions
If a = 4, b = (7 - a) = 3
a^4 - b^4 = 4^4 - 3^4 = 256 - 81 = 175
If a = 3, b = 4
a^4 - b^4 = 3^4 - 4^4 = 81 - 276 = -175
Similar questions