Sam has £480. he spends 1/4 of £480. work out how much money sam has left

Step-by-step explanation:

to find the arithmetic sequence with a4=-1 and a6=-13

first: find the difference: an=a+(n-1)d

a4=-1

that means a1+d(4-1)=-1 ( since a4 given and need to find a1)

a1+3d=-1 first equation

a1+d(6-1)=-13 ( a6 is given)

a1+5d=-13 second equation

a1+3d=-1

a1+5d=-13 ( find a and d by subtraction)

a1+3d-a1-5d=-1-(-13)

2d=12

d=-12/2=-6 ( substitute d in the equation: a1+3d=-1)

difference =-6

a1=17

a1,a2,a3,a4,a5,a6,

the sequence is : 17,11,5,-1,-7,-13,

hope it works