Using the "complete the square" method, solve the following x^2 +4x - 21 =0
x2+4x-21= 0, This can be factorised into brackets as shown: (x+2)2 - 4 - 21 = 0 SImplified, so all x's are on one side of the equation: (x+2)2 = 25, Removing square root, DONT FORGET "±" : (x+2) = ± 5, Solve for two solutions: x = 3, x = -7
CS
Related Maths A Level answers
All answers ▸How do I differentiate an expression of the form y = (ax+b)^n?
a) Solve the following equation by completing the square: x^(2)+ 6x + 1= 0. b) Solve the following equation by factorisation: x^(2) - 4x - 5 = 0 c) Solve the following quadratic inequality: x^(2) - 4x - 5 < 0 (hint use your answer to part b)
The line AB has equation 3x + 5y = 7 (a. Find the gradient of AB)
i) Using implicit differentiation find dy/dx for x^2 + y^2 = 4 ii) At what points is the tangent to the curve parallel to the y axis iii) Given the line y=x+c only intersects the circle once find c given that c is positive.