Excellent work as always however, you missed a solution. If you take ordered pair (a,b) = (2,8), the expression 3a - 9b evaulates to 3(a) - 9(b) = 3(2) - 9(8) = 6 - 72 = -66
Thank you for explaining. There are 3 cases, but only 2 cases are done in the video. The rest case is a=2 and b=8. As for it, 3a-9b = 3×2-9×8 = -66. Therefore, there are 3 solutions /values. [ 3a-9b = 6, 24, -66 ]
There are actually three possible values sir! Try to solve the problem by first making any of the variables in equation two subject of formula and then substituting the result into equation one.
E = 3a - 9b a + b = u u² - 2u - 80 = 0 u = (2 ± 18)/2 => u = 10 ∨ u = -8 [ (u - 10)(u + 8) = 0 ] u = 10 => a + b = 10 ab = 16 => (a, b) = {(2, 8); (8,2)} => *E = -66* ∨ *E = 6* u = -8 => a + b = -8 ab = 16 => (a, b) = {(-4, -4)} => *E = 24*
Excellent work as always however, you missed a solution. If you take ordered pair (a,b) = (2,8), the expression 3a - 9b evaulates to
3(a) - 9(b)
= 3(2) - 9(8)
= 6 - 72
= -66
Thank you for explaining. There are 3 cases, but only 2 cases are done in the video. The rest case is a=2 and b=8.
As for it, 3a-9b = 3×2-9×8 = -66. Therefore, there are 3 solutions /values. [ 3a-9b = 6, 24, -66 ]
Case1: we have (-66)
Case2: we have (6)
Case3: we have (24)
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There are actually three possible values sir! Try to solve the problem by first making any of the variables in equation two subject of formula and then substituting the result into equation one.
E = 3a - 9b
a + b = u
u² - 2u - 80 = 0
u = (2 ± 18)/2 => u = 10 ∨ u = -8
[ (u - 10)(u + 8) = 0 ]
u = 10 => a + b = 10
ab = 16
=> (a, b) = {(2, 8); (8,2)}
=> *E = -66* ∨ *E = 6*
u = -8 => a + b = -8
ab = 16
=> (a, b) = {(-4, -4)}
=> *E = 24*