How do you solve the quadratic X^2 - 8X + 15 = 0 ?
First factorise (using a "farmer's field", will draw this on whiteboard):=> (X-3)(X-5) = 0Hence using the zero rule (one of the brackets must be equal to 0 if the product is 0),either X-3 = 0 OR X-5=0=> X=3 or X=5Check by substituting back into the original equation:(3)^2 - 8(3) + 15 = 09 - 24 + 15 = 0-15 + 15 = 0 (correct)and(5)^2 - 8(5) +15 = 025 - 40 +15 = 0-15 + 15 = 0 (correct).
SJ
Related Maths GCSE answers
All answers ▸Find the equation of a straight line that passes through the points (2,7) and (5,3)
How to apply the quadratic equation
ABCDEFGH is a cuboid. AB=5.6 cm CH=7.2cm. Angle BCA=44degrees. Find the size of the angle between AH and the plane ABCD giving your answer correct to one dp.
Josie is paid £1200 per month. She is going to receive an increase of 4% in the amount she is paid. Work out how much money Josie we be paid each month after the increase.