Does the equation: x^2+5x-6 have two real roots? If so what are they?

Having two real roots is equivalent to having two intersections with the x axis.

The equation is a parabola (a U shape) so, having two real roots is equivalent to having the lowest point of the curve below the x axis.

By differentiation we have that 2x+5 is the rate of change, and setting this equal to zero gives the stationary point x=-5/2.

Using the equation we then have:

y=(-5/2)2+5(-5/2)-6=-12.25

This shows that the minimum point of the curve is (-5/2,-12.25) which is below the x axis.

Thus, there are two real roots and applying the quadratic formula gives the values: -6 and 1.

Where the quadratic formula is:

[-b+sqrt(b2-4ac)] / [2a] and [-b-sqrt(b2-4ac)] / [2a]

Answered by Stephen B. Maths tutor

3840 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Find X log(x)=4 Base 10


How do i remember the difference between differentiation and integration?


How do I find the maxima and minima of a function?


What is the product rule and when do you use it?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2024

Terms & Conditions|Privacy Policy