Question

need help solving this equation (x-4)(2x+5)=0

Answer 1

you want to obtain the values of x?

Answer 2

The thing is either of the two expressions x-4=0 or 2x+5=0
x=4 or 2x=-5, i.e.
x=4, or x=-5/2

Answer 3

thanks :)

Answer 4

(x-4)(2x+5)=0

Multiply each term of inside the first parenthesis to each term in the second parenthesis and add:

2x^2 + 5x - 8x -20 = 0

2x^2 + 13x -20 = 0 thiis is a quadratic equation

you can use the formula:

x = [-b +- (b^2 - 4ac)^1/2] / 2a

a = 2, b = 13, c = 20

Remember, you will get two solutions x1 and x2

x1 = [-2 + (169 - 4*2*20)^1/2]/4 = [-2 + (169 - 160)^1/2]/4 = (-2 + 9^1/2)/4
= (-2 + 3)/4 = 1/4

x2 = [-2 - (169 - 4*2*20)^1/2]/4 = [-2 - (169 - 160)^1/2]/4 = (-2 -3)/4 = -5/4

Sorry

2x^2 + 5x - 8x -20 = 0 is 2x^2 - 3x -20 = 0

the quadratic equation is:

2x^2 - 3x -20 = 0

a = 2
b= -3
c= -20