4
algebra

Rearrange to standard form and solve: {y=3x52x+y=15\begin{cases} y = 3x - 5 \\ 2x + y = 15 \end{cases}

A

(5,10)(5, 10)

B

(3,4)(3, 4)

C

(4,7)(4, 7)

D

(6,13)(6, 13)

Correct Answer: C

Choice C is the correct answer. First, let's rearrange the first equation to standard form.

Step 1: Rearrange y=3x5y = 3x - 5 to standard form: 3x+y=5-3x + y = -5 or 3xy=53x - y = 5

Step 2: Now we have: {3xy=52x+y=15\begin{cases} 3x - y = 5 \\ 2x + y = 15 \end{cases}

The yy terms are opposites, so add: 5x=205x = 20x=4x = 4

Step 3: Substitute x=4x = 4 into the second equation: 2(4)+y=152(4) + y = 158+y=158 + y = 15y=7y = 7

Solution: (4,7)(4, 7)

Verification: 7=3(4)5=125=77 = 3(4) - 5 = 12 - 5 = 7

💡 Strategic Tip: Converting to standard form (Ax+By=C)(Ax + By = C) often reveals elimination opportunities.

Choice A is incorrect because2(5)+10=20 eq152(5) + 10 = 20 \ eq 15.

Choice B is incorrect because2(3)+4=10 eq152(3) + 4 = 10 \ eq 15.

Choice D is incorrect because2(6)+13=25 eq152(6) + 13 = 25 \ eq 15.