Question

Solve 2x^2 - x ≥ 15. Show your work

Answer 1

x ∈ 〈-∞,-5/2]∪[3,+∞〉

Explanation:

2x²-x-15 ≥ 0

2x²+5x-6x-15 ≥ 0

x(2x+5)-3(2x+5) ≥ 0

(2x+5)(x-3) ≥ 0

so

2x+5 ≥ 0

x-3 ≥ 0

2x+5 ≤ 0

x-3 ≤ 0

solve the equation

x ≥ -5/2

x ≥ 3

x ≤ -5/2

x ≤ 3

x ∈ [3,+∞〉

x ∈ 〈-∞,-5/2]

so x ∈ 〈-∞,-5/2]∪[3,+∞〉