SAT Math · Linear equations in one variable · medium

For what value of k does the equation 6(x-1) + 9 = kx + 7 have no solution?

For what value of kk does the equation 6(x−1)+9=kx+76(x-1) + 9 = kx + 7 have no solution?

Answer and explanation

Answer: D: 6

Simplify the left side: 6(x−1)+9=6x−6+9=6x+36(x - 1) + 9 = 6x - 6 + 9 = 6x + 3, so the equation is 6x+3=kx+76x + 3 = kx + 7. It has no solution when the xx-coefficients match but the constants differ. With k=6k = 6, the equation becomes 6x+3=6x+76x + 3 = 6x + 7, or 3=73 = 7, which is false for every xx. So k=6k = 6, choice D. Choice A (7) is the constant on the right side. Choice B (9) is the constant added on the left before distributing. Choice C (−6-6) has the wrong sign and gives the solution x=13x = \frac{1}{3}.

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