Diketahui fungsi f(x)=ax + b. Jika f(−2)= −11 dan f(4)=7, nilai a x b adalah
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Nilai a × b adalah -15
Langkah langkah
f(x) = ax + b
f(-2) = -11
f(-2) = a(-2) + b
-11 = -2a + b
-2a + b = -11
f(4) = 7
f(4) = a(4) + b
7 = 4a + b
4a + b = 7
Eliminasi f(-2) dan f(4)
-2a + b = -11
4a + b = 7
___________--
-6a = -18
a = -18/-6
a = 3
Subsitusi a ke f(4)
4a + b = 7
4(3) + b = 7
12 + b = 7
b = 7 - 12
b = -5
Nilai a × b
= 3 × (-5)
= -15
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