1i) solve x^2-4x-21=0
Factorise to get (x+3)(x-7)=0
So you can see that x = -3 or x =7
KI
Related Maths GCSE answers
All answers ▸Solve the simultaneous equations for x and y: 3x+2y = 14 and 5x-y = 6
Factorise 3x + 6
Find the equation of the line that passes through (2, 4) and (7, -11)
Anna has 6 bananas. Ben has 2.5 times more bananas than Anna. Callum has a third as many bananas as Anna and Ben have together. How many bananas do Anna, Ben and Callum have together?