X^2 + 4x -21
= (x +7)(x - 3)
hope that helps
Answer:
x = 8
Step-by-step explanation:
If the number 212x5 is a multiple of 3, the sum of the digits needs to be a multiple of 3, so we have:
2 + 1 + 2 + x + 5 = 10 + x
The value of x can be 2, 5 or 8
If the number is a multiple of 11, we have to calculate the first number minus the second, plus the third, minus the fourth... and so on, and the result needs to be a multiple of 11. So we have:
2 - 1 + 2 - x + 5 = 8 - x
x needs to be 8, so we have 8 - 8 = 0, that is a multiple of 11.
So the value of x is 8.
Simplifying
10 + 5x = 5x + 10
Reorder the terms:
10 + 5x = 10 + 5x
Add '-10' to each side of the equation.
10 + -10 + 5x = 10 + -10 + 5x
Combine like terms: 10 + -10 = 0
0 + 5x = 10 + -10 + 5x
5x = 10 + -10 + 5x
Combine like terms: 10 + -10 = 0
5x = 0 + 5x
5x = 5x
Add '-5x' to each side of the equation.
5x + -5x = 5x + -5x
Combine like terms: 5x + -5x = 0
0 = 5x + -5x
Combine like terms: 5x + -5x = 0
0 = 0
Solving
0 = 0
Answer: 0 solutions
Add 10 to both sides. X is 2. A.
