factorise x^2+10x+21
firstly the largest power is x^2 so when factorising we know that both brackets must involve an x plus or minus a number.
next we look at the 21 and we need two numbers that multiply together to get this number, the two sets of numbers that multiply to get this is 1 and 21 and 3 and 7.
then we take these two sets of numbers and we look at the 10x this means the numbers must add/subtract to give ten, this means the answer must use the 3 and 7 as they add to give 10
therefore our answer is (x+3)(x+7)
RC
Related Maths GCSE answers
All answers ▸at a shop in the US tax is added onto the price of an item at the till. this shop adds 5.7% of the items value to the total cost. if you buy a ball priced as $15, how much will you have to pay ?
Factorise x^2-7x+12
What is 45% of 60?
(This was taken from a GCSE past paper)A bag of 24 spoons costs £19.95. A box of 18 forks costs £15.55. Bags and boxes cannot be split. Gregor decides to buy the same number of spoons as forks. He places an order to buy the smallest number of each