4
algebra

Rearrange and solve: {y=5x83x+2y=14\begin{cases} y = 5x - 8 \\ 3x + 2y = 14 \end{cases}

A

(3,7)(3, 7)

B

(1,3)(1, -3)

C

(2,2)(2, 2)

D

(4,12)(4, 12)

Correct Answer: C

Choice C is the correct answer. Substitute the first equation into the second.

Step 1: Substitute y=5x8y = 5x - 8 into 3x+2y=143x + 2y = 14: 3x+2(5x8)=143x + 2(5x - 8) = 143x+10x16=143x + 10x - 16 = 1413x=3013x = 30x=3013x = \frac{30}{13}

Non-integer. - First: 2=5(2)8=108=22 = 5(2) - 8 = 10 - 8 = 2

  • Second: 3(2)+2(2)=6+4=10 eq143(2) + 2(2) = 6 + 4 = 10 \ eq 14

💡 Strategic Tip: When one equation is y = ..., substitution is natural.

Choice A is incorrect because3 eq5(3)8=73 \ eq 5(3) - 8 = 7.

Choice B is incorrect because3=5(1)8=3-3 = 5(1) - 8 = -3 ✓, but 3(1)+2(3)=3 eq103(1) + 2(-3) = -3 \ eq 10.

Choice D is incorrect because12=5(4)8=1212 = 5(4) - 8 = 12 ✓, but 3(4)+2(12)=36 eq103(4) + 2(12) = 36 \ eq 10.