well, you know that x^2 - 7x = 30
so solve that in the usual way
If 7× a number is subtracted from the square of the number the result is 30 find the number
4 answers
let y = the number
Then y^2 - 7*y = 30
y^2 -7y -30 = 0
(y - 10)(y + 3) = 0
So y = 10 and -3. The -3 make no sense so y = 10
Then y^2 - 7*y = 30
y^2 -7y -30 = 0
(y - 10)(y + 3) = 0
So y = 10 and -3. The -3 make no sense so y = 10
Why reject the 2nd answer, it did not classify the numbers
(-3)^2 - 7(-3)
= 9 + 21
= 30
(-3)^2 - 7(-3)
= 9 + 21
= 30
Yikes! Now it makes sense. Problems like this that I usually work I'm looking for a volume or a mass and a mass of -3 g or a volume of -3 cc doesn't make sense. I needed to get in the math bubble to make sense of it. Thanks.
4 answers