Question

x2 – 10x + 21 write in notebook​

Answer 1

x² - 10x +21

= x² +( 7 +3 )x + 21

= x² + 7x +3x + 21

= x(x + 7) + 3(x+ 7)

= (x+ 3)(x + 7)

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Answer 2

Answer:

(x+3)(x+7)

Step-by-step explanation:

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)