Find values of x which satisfy the inequality: x^2-4x-2<10

We first apply a simple addition to make the inequality 0 on one side. We subtract 10, giving x^2-4x-12<0. Now we factorise the equation in x, intuitively or using the quadratic formula: x=(-b+sqrt(b^2-4ac))/2a or X==(-b-sqrt(b^2-4ac))/2a to give 2 values for x. In this case we can use intuition to get (X-6)(X+2)<0. We draw a graph of the function and deduce which values of X satisfy the inequality. Here, if -2 < x < 6 the inequality is satisfied.

RK

Related Further Mathematics A Level answers

All answers ▸

Why is the argument of a+bi equal to arctan(b/a)?


Solve the differential equations dx/dt=2x+y+1 and dy/dt=4x-y+1 given that when t=0 x=20 and y=60. (A2 Further pure)


Find the equation of the tangent to the curve y = exp(x) at the point ( a, exp(a) ). Deduce the equation of the tangent to the curve which passes through the point (0,1) .


Find the cube roots of unity.