Posted by **Tomtom** on Thursday, November 17, 2011 at 6:52pm.

Help trig question involving discriminant?

a)Find the value of the discriminant.

b)Use any method to find the real roots of the equation if they exist.

2x^2+7x=0

- Trigonometry -
**Steve**, Friday, November 18, 2011 at 12:05pm
surely you got as far as evaluating the discriminant: b^2 - 4ac = 7 - 0 = 7

factor: x(2x+7) = 0

a product is zero if any factor is zero. So,

x=0 or (2x+7) = 0

so, the roots are 0 and -7/2

Using the quadratic formula, we have

x = [-7 +/- sqrt(49-0)]/4

= [-7 +/- 7]/2

= 0 or -7/2

Completing the square,

2(x^2 + 7/2 x + (7/4)^2) - 2(7/4)^2 = 0

2(x + 7/4)^2 = 2(7/4)^2

x + 7/4 = (7/4)^2 = 49/16

x = -7/4 +/- 7/4

= 0 or -7/2

## Answer this Question

## Related Questions

- math - I HAVE THESE ANSWERS FOR THE PROBLEMS. COULD YOU DOUBLE CHECK PLEASE, ...
- math - Could you please solve so I can double check my answers for the practice ...
- Calculus/pre-trig - Write the formula for the discriminant. State the types of ...
- math - How many real roots exist if the discriminant of the equation=0?
- Algebra Problem - State the value of the discriminant and the number of real ...
- algebra - What would be the discriminant for this equation: x^2-2x+12=0 How many...
- Math - For the following equation, state the value of the discriminant and then ...
- trig - use the discriminant to solve for the smallest value of b that would make...
- maths2 - Use the discriminant to determine the number of real roots the equation...
- mathematics - Use the discriminant to determine the number of real roots the ...

More Related Questions