Tolong jawab no 10 dengan caranya

f(x) = bx²+ax+4
g(x) = ax²+bx+4

f'(2) = -9
g'(-2) = -15
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f(x) = bx²+ax+4
f'(x) = 2bx+a

g(x) = ax²+bx+4
g'(x) = 2ax+b
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f'(x) = 2bx+a
f'(2) = 2b.2+a
-9 = 4b+a... pers.1

g'(x) = 2ax+b
g'(-2) = 2a.-2+b
-15 = -4a+b... pers.2
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a+4b = -9 |×4|
-4a+b = -15 |×1|
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4a+16b = -36
-4a+b = -15
------------------- (+)
17b = -51
b = -51/17
b = -3

subtitusi ke a+4b = -9
a+4b = -9
a+4.(-3) = -9
a+ -12 = -9
a = -9+12
a = 3
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jadi a+b yg memenuhi yaitu,
a+b = 3+(-3)
= 0