Negative three times a number plus four is no more than the number minus eight. What is the number?

2 Answers
Jun 28, 2018

number nn is such that n>=3n3

Explanation:

Let the number be nn

Three times the number is -3 xx n3×n = 3n3n

Plus four is -3n +43n+4

Number minus eight is n - 8n8

No more than is <=

So we get:

-3n+4 <= n - 83n+4n8

Simplify and solve this linear equation:

-3n-n <= -8-43nn84

-4n <= -124n12

n >= -12/-4n124

n >= 3n3

So the number nn is such that n>=3n3

Hope this helps!

Jun 28, 2018

See a solution process below:

Explanation:

"a number" -> nn

"Negative three times a number" -> -3n3n

"Negative three times a number plus four" -> -3n + 43n+4

"is no more than" -> <= giving:

-3n <=3n

"the number minus eight" -> n - 8n8 giving:

-3n + 4 <= n - 83n+4n8

Next, subtract color(red)(n)n and color(blue)(4)4 from each side of the inequality to isolate the nn term while keeping the inequality balanced:

-3n - color(red)(n) + 4 - color(blue)(4) <= n - color(red)(n) - 8 - color(blue)(4)3nn+44nn84

-3n - color(red)(1n) + 0 <= 0 - 123n1n+0012

(-3 - color(red)(1))n <= -12(31)n12

-4n <= -124n12

Now, divide each side of the inequality by color(blue)(-4)4 to solve for nn while keeping the inequality balanced. However, because we are multiplying or dividing an inequality by a negative number we must reverse the inequality operator.

(-4n)/color(blue)(-4) color(red)(>=) (-12)/color(blue)(-4)4n4124

(color(blue)(cancel(color(black)(-4)))n)/cancel(color(blue)(-4)) color(red)(>=) 3

n >= 3