4 times a number is 21 less than the square of that number. Find the positive solution.

Let x = your number.

4x = x^2 - 21. Subtract 4x from both sides.

0 = x^2 - 4x - 21. Factor.

0 = (x - 7) (x + 3). Set both terms equal to zero.

(x + 3) = 0. Subtract 3 from both sides.

x = -3. This is the negative solution.

(x - 7) = 0. Add 7 to both sides.

x = 7. This is the positive solution

the equivalent expression are always the hardest ones but you look at the gcf also

step-by-step explanation:

answer: bearing in mind that a rectangle has a perimeter of length + length + width + width.

step-by-step explanation:

p = perimeter

l = length

x=width

p = 2l + 2x

p = 2(l+x)     < ==== perimeter of the base of the box.