First of all, we can observe that
So the expression becomes
This means that the expression is defined for every
Now, since the denominator is always positive (when it exists), the fraction can only be positive if the denominator is also positive: we must ask
Since we can't accept 3 as an answer, the actual solution set is
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 )