How many roots does the equation x^2 = x + 12 have and what are they?

x2 -x -12 = 0. Here we have rearranged the equation so that we have 0 on one side of the equation, allowing us to now factorise. (x - 4)(x+3) = 0. By looking at the equation we can see that the number 12 has 3 multiplying factor couples; 1 and 12; 2 and 6; 3 and 4. The minus sign can be used interchangeably on the factor couples to produce the result of -12. Of the three couples, only one can produce a result of -x when the brackets are multiplied out. Hence the desired factor couple is +3 and -4. (x-4) = 0 or (x+3) = 0. Hence, x = 4 or x = -3. If we treat the two brackets as 'a' and 'b', the equation becomes a x b = 0. This would mean either 'a' or 'b' is 0. We can therefore use an "or" scenario to find that x is either 4 or -3. As a result, the equation has two distinct real roots, 4 and -3.

JE

Related Maths A Level answers

All answers ▸

Given f(x) = (x^4 - 1) / (x^4 + 1), use the quotient rule to show that f'(x) = nx^3 / (x^4 + 1)^2 where n is an integer to be determined.


https://1drv.ms/w/s!Ajvn5XL_gYTXgaZeAS-K7z62VSxjYw?e=lnAZLx


Find the set of values of x for which x(x-4) > 12


What is differentiation and integration?