Equation Equivalency
1. **Problem 38:** Find which equation is equivalent to $y - 34 = x(x - 12)$.
Start by expanding the right side:
$$ y - 34 = x^2 - 12x $$
Add 34 to both sides:
$$ y = x^2 - 12x + 34 $$
Now check each option:
(a) $y = (x - 17)(x + 2) = x^2 + 2x - 17x - 34 = x^2 - 15x - 34$ (not equal)
(b) $y = (x - 6)^2 + 2 = (x^2 - 12x + 36) + 2 = x^2 -12x + 38$ (not equal)
(c) $y = (x - 6)^2 - 2 = (x^2 - 12x + 36) - 2 = x^2 - 12x + 34$ (matches)
(d) $y = (x - 17)(x - 2) = x^2 - 2x - 17x + 34 = x^2 - 19x + 34$ (not equal)
Answer: (c)
2. **Problem 39:** Identify which pair of equations could not solve
$$\begin{cases} 4x + 2y = 22 \\ -2x + 2y = -8 \end{cases}$$
Check if each pair is equivalent or can be transformed into the original.
(a) Changes second equation sign: $2x - 2y=8$ is not equivalent to $-2x + 2y = -8$
(b) Second equation multiplied by 2: $-4x + 4y = -16$ from $-2x + 2y = -8$ (valid)
(c) Both equations multiplied by 3: $12x + 6y = 66$ and $6x - 6y = 24$ (valid)
(d) First doubled: $8x + 4y = 44$ and double second with sign flipped: $-8x +8y = -16$ vs given $-8x + 8y = -8$ (not matching)
Answer: (a) and (d) pairs do not preserve equivalency, but question asks which could not be used. (a) is incorrect because second equation is reversed sign and value.
So answer: (a)
3. **Problem 40:** Translate 'sixty more than 9 times a number is 375'
This means $9h + 60 = 375$
Answer: (a)
4. **Problem 41:** Solve $\frac{3}{5}(x + 2) = x - 4$
Multiply both sides by 5:
$$3(x + 2) = 5x - 20$$
Expand:
$$3x + 6 = 5x - 20$$
Bring terms together:
$$6 + 20 = 5x - 3x$$
$$26 = 2x$$
$$x = 13$$
Answer: (b)
5. **Problem 42:** Solve $x^2 - 6x = 0$
Factor:
$$x(x - 6) = 0$$
Solutions:
$$x = 0$$ or $$x = 6$$
Answer: (c)
6. **Problem 43:** Three brothers ages are consecutive even integers. Let youngest be $x$.
Oldest is $x + 4$ (since even consecutives, step 2).
Condition: $3x = x + 4 + 48$
Solve:
$$3x = x + 52$$
$$2x = 52$$
$$x = 26$$
Answer: (d)
7. **Problem 44:** Two numbers sum to 47 and difference is 15.
Let larger = $x$, smaller = $y$
$$x + y = 47$$
$$x - y = 15$$
Add equations:
$$2x = 62
ightarrow x = 31$$
Answer: (c)
8. **Problem 45:** Expression undefined if denominator zero:
$$2n - 1 = 0
ightarrow n = \frac{1}{2}$$
Answer: (d)
9. **Problem 46:**
Define $C$ = Chartered class students.
Professional = $C + 60$
Graduate = $2C - 50$
Fundamental = $3C$
Total:
$$C + (C + 60) + (2C - 50) + 3C = 1424$$
Sum:
$$C + C + 60 + 2C - 50 + 3C = 1424$$
$$7C + 10 = 1424$$
$$7C = 1414$$
$$C = 202$$
Answer: (b)
10. **Problem 47:** Solve $f(x) = h(x)$:
$$\frac{1}{2}x + 3 = |x|$$
Consider cases:
Case 1: $x \geq 0$
$$\frac{1}{2}x + 3 = x$$
$$3 = x - \frac{1}{2}x = \frac{1}{2}x$$
$$x = 6$$ (not in options)
Case 2: $x < 0$
$$\frac{1}{2}x + 3 = -x$$
$$\frac{1}{2}x + x = -3$$
$$\frac{3}{2}x = -3$$
$$x = -2$$ (in options)
Answer: (a)
Final answers:
38: (c)
39: (a)
40: (a)
41: (b)
42: (c)
43: (d)
44: (c)
45: (d)
46: (b)
47: (a)