So you have the two equations a − b + c = −18 and a + b + c = 10. If you subtract the
corresponding sides of the equation a − b + c = −18 from the corresponding sides of the
equation a + b + c = 10, the a and c terms will cancel each other out, and you will be left with
an equation with just the variable b.
30 . E
The square of any number is nonnegative. So x^2 ≥ 0 for all real x. Then x^2 + 3 > 0 for all real x.
The radical symbol is defined for any nonnegative number. So function f(x) is defined for
all real x. Remember that if y > 0, the mathematical convention is that means the
positive square root of y. Also, .
31 . C
The vertical dimension of the shaded rectangle whose horizontal dimension is on the x-axis
for 3 ≤ x ≤ 6 is
The area of this shaded rectangle is 20(3) = 60.
The vertical dimension of the shaded rectangle whose horizontal dimension is on the x-axis
for 6 ≤ x ≤ 9 is
The area of this shaded rectangle is 15(3) = 45.
The vertical dimension of the shaded rectangle whose horizontal dimension is on the x-axis
for 9 ≤ x ≤ 12 is