solve this equation using the quadratic formula; 2x^2 + x = 15

Question

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Answer 1

2x² + x = 15

2x² + x - 15 = 0

(2x - 5) (x + 3) = 0

 

If the product of the two expressions is zero, then one or both of the factors must be zero. Find those values of x that make each factor equal to zero:

 

2x -5 = 0

2x = 5

x = 5/2

 

x + 3 = 0

x = -3

 

x = -3, and x = 5/2

 

Answer 2

ax^2 + bx + c = 0
D = b^2 - 4ac
x₁₂ = (- b ± √D) / 2a


2x^2 + x - 15 = 0

a = 2, b = 1, c = - 15

D = 1 + 120 = 121

x₁₂ = (- 1 ± √121) / 4

x₁ = (- 1 + 11) / 4 = 5/2 = 2.5 

x₂ = (- 1 - 11) / 4 = - 3