Solving Quadratics

Solving Quadratics

1. s2+2s-80

   • We now factorise
     • The 2 numbers in the bracket will be positive and negative
       • If the number term in the equation is positive, both the brackets will be positive
         • If it is negative, one bracket will be positive and one negative
       • We can start writing our answer...
         • (s )(s )
           • We know s will be at the start of both brackets as it is the squared term
           • We then need to work out which numbers are in the bracket
             • Find two numbers that times to make the number term(-80)
               • 10&8, 2&40, 5&16...
                 • Find a pair of those numbers that also add to make the x term(2s)
                   • 10 and -8 work!
                     • Now put these into your brackets...
                       • (s+10)(s-8)
                         • To solve this, we have to say that it equals 0
                           • (s+10)(s-8)=0
                             • Take the (s+10) bracket
                               • If (s+10)=0, then s=0-10..
                                 • And 0-10=-10
                                   • And the other part of the brackets...
                                     • (s-8)=0
                                       • becomes...
                                         • s=0+8=8
                                           • You just reverse the signs of the number terms in the bracket!
                                             • So our solutions are...
                                               • s=-10 OR s=8
                                                 • We have to write OR not AND as the solution can't be both at the same time
                                                   • If in doubt, just write your solutions and nothing else
                                                     • s=-10 s=8
                 • Remember that one number in these pairs will be negative