The expression 7•3x is not equal to the expression 21x. You might think that the two expressions are the same since 7x3 is 21 but the first expression is a dot product. This kind of expression includes the magnitude and direction of the vector in an expression, for example, <span>7•3x. The second expression, 21x, expresses only the magnitude and does not include the direction.</span>
Answer:
x=0.5355 or x=-6.5355
First step is to: Isolate the constant term by adding 7 to both sides
Step-by-step explanation:
We want to solve this equation: 
On observation, the trinomial is not factorizable so we use the Completing the square method.
Step 1: Isolate the constant term by adding 7 to both sides

Step 2: Divide the equation all through by the coefficient of
which is 2.

Step 3: Divide the coefficient of x by 2, square it and add it to both sides.
Coefficient of x=6
Divided by 2=3
Square of 3=
Therefore, we have:

Step 4: Write the Left Hand side in the form 

Step 5: Take the square root of both sides and solve for x

Answer:
<em>The second choice is correct. It can be factored as:</em>

Step-by-step explanation:
<u>The Difference of Squares Method for Factoring</u>
The expression:

Is a widely used method to factor binomials that are expressed as the subtraction of two perfect squares.
The condition for a binomial to be factored by using this method is that both terms must have an exact square root and they must be subtracted.
The last two choices are not valid because they are not a subtraction but an addition.
The first choice is not valid because none of the terms is a perfect square.
The second choice is correct. It can be factored as:

How much of each solution should the teacher mix together to get 105 ML of 60% sugar solution for an experiment?
1. Look at how 60% is closer to the solution of lower concentration (50%). You can deduce that you will be mixing a higher volume of the 50% solution.
2. All 4 answers add up to 105ml.
3. The intuitive answer is the first option:
70 ML of the 50% solution and 35 ML of the 80% solution
4. Let's check whether point 3 is true.
70ml/105ml X 0.5 + 35ml/105ml X 0.8 = (35 + 28)/105= 63/105= 60% / 105 ml = 105ml of 60% sugar solution