KUNCI JAWABAN Matematika Kelas 10 Semester 2, Uji Kompetensi 7.1 Hal 13: Akar-akar Persamaan Kuadrat

eliminasi,
a⊃2; - ab + b⊃2; = 49
a⊃2; + 2ab + b⊃2; = 169
_____________________ ( - )
-3ab = -120
ab = -120/-3
ab = 40

dan perhatikan bahwa :
(a - b)⊃2; = (a + b)⊃2; - 4ab, maka
(a - b)⊃2; = (13)⊃2; - 4(40)
(a - b)⊃2; = 169 - 160 = 9
 
9. Faktorkan: 4kn + 6ak + 6an + 9a2.

Jawab:

4kn + 6ak + 6an + 9a⊃2; = (4kn + 6ak) + (6an + 9a⊃2;)
                                       = 2k (2n + 3a) + 3a (2n + 3a)

                                       = (2k + 3a) (2n + 3a)

10. Jika a + b + c = 0 dengan a, b, c ≠ 0, tentukan nilai [a(1/b + 1/c) + b(1/c + 1/a) + c(1/a + 1/b)] ⊃2;

Jawab:

[a(1/b + 1/c) + b(1/c + 1/a) + c(1/a + 1/b)] ⊃2; =
(a/b + a/c + b/c + b/a + c/a + c/b )⊃2; = 
[(b/a + c/a) + (a/b + c/b ) + (a/c + b/c )]⊃2; = 
[ -a/a + -b/b + -c/c ]⊃2; = [ -1 -1 -1]⊃2; = (-3)⊃2; = 9

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