The cost of 6 comic books is
1 answer:
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Answer:
(- 2, 15 ) and (2, 7 )
Step-by-step explanation:
Given the 2 equations
y = 3x² - 2x - 1 → (1)
2x + y = 11 → (2) ← subtract 2x from both sides
y = 11 - 2x → (3)
Substitute y = 3x² - 2x - 1 into (3)
3x² - 2x - 1 = 11 - 2x ( subtract 11 - 2x from both sides )
3x² - 12 = 0 ( add 12 to both sides )
3x² = 12 ( divide both sides by 3 )
x² = 4 ( take the square root of both sides )
x = ± = ± 2
Substitute these values into (3) for corresponding values of y
x = - 2 : y = 11 - 2(- 2) = 11 + 4 = 15 ⇒ (- 2, 15 )
x = 2 : y = 11 - 2(2) = 11 - 4 = 7 ⇒ (2, 7 )