"The product of two numbers is 360. If one number is 16 less than double the other number, find the two possible number pairs."
This is my working:
x(2x-16)= 360
2x2-16x= 360
2x2-16x-360= 0
2(x2-8x-180)= 0
2(x-18)(x+10)= 0
x = 18 or -10
First pair: 18 and 10 (changing the ten from negative to positive)
I thought the second pair was just -18 and -10 but the textbook says -10 and -36. The quadratic formula of course just returns the same result as the factorisation above. I'm not sure how to arrive at the textbook's answer.
This is my working:
x(2x-16)= 360
2x2-16x= 360
2x2-16x-360= 0
2(x2-8x-180)= 0
2(x-18)(x+10)= 0
x = 18 or -10
First pair: 18 and 10 (changing the ten from negative to positive)
I thought the second pair was just -18 and -10 but the textbook says -10 and -36. The quadratic formula of course just returns the same result as the factorisation above. I'm not sure how to arrive at the textbook's answer.