Given that x^2+10x+3 can be written in the form (x+a)^2+b, find the values of a and b.

We can tackle this question by completing the square. Completing the square allows us to write a quadratic equation (x^2+10x+3) in the simpler form (x+a)^2+b.To complete the square, first we need to find the value of our a. To find the value of our a we need to halve the x term coefficient (halve the number in front of the x). In this question, the number in front of our x is 10 so our a value must be 5.We can then substitute this value of a into our completing the square equation: (x+5)^2+b.To find our b value we need to expand out (x+5)^2 + b and compare this to our original equation.If we expand (x+5)^2 + b we get x^2 + 10x + 25 + b. However, looking at our original equation we know our x^2 and x terms are correct but the constant (the term with no x's) we should be left with is 3 but instead we are left with 25 + b. Hence, 25 + b = 3 (as these are the only terms without x's) so b = -22.Thus, we can write the equation x^2+10x+3 as (x+5)^2 -22 so a = 5 and b = - 22.

Answered by Katie C. Maths tutor

7313 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

y = (x + 2)(x + 5)


If x:y = 7:4 and x+y = 88 , work out the value of x–y.


The second term of an arithmetic sequence is 7. The sum of the first four terms of the arithmetic sequence is 12. Find the first term, a, and the common difference, d, of the sequence.


How to expand brackets?


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