Question

Diketahui akar-akar persamaan kuatrat:
-2x²+12x-15=0 adalah x1 dan x2. Nilai x1²+x2² adalah..
A. 16
B. 21
C. 36
D. 46
E. 66

Answer 1

Verified answer

Kelas 10 Matematika
Bab Trigonometri

-2x² + 12x - 15 = 0
a = -2; b = 12; c = -15

(x1)² + (x2)²
= (x1 + x2)² - 2 . x1 . x2
= (-b/a)² - 2 . c/a
= (-12/-2)² - 2 . -15/-2
= 36 - 15
= 21

Answer 2

¤ X1 + X2 = -b/a = -12/-2 = 6
¤ X1 × X2 = c/a = -15/-2 = 15/2

X1^2 + X2^2 = (X1 + X2)^2 - 2. X1 × X2
= 6^2 - 2× 15/2
= 36 - 15
= 21

jawabannya B
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