Question

Line QR goes through points Q(0, 1) and R(2, 7). Which equation represents line QR?

y – 1 = 6x
y – 1 = 3x
y – 7 = 2x – 6
y – 7 = x – 2

Answer 1

b

Explanation:

Answer 2

We write the equation in the form of directional.

y -1 = 6x ⇔ y = 6x + 1
y - 1 = 3x ⇔ y = 3x + 1
y - 7 = 2x - 6 ⇔ y = 2x - 6 + 7
y = 2x + 1
y - 7 = x - 2 ⇔ y = x - 2 + 7
y = x + 5

Equations cleverly arranged .
Point Q = (0,1)
b factor , not only fits the last equation
In the drawing have engraved points Q and R are tangent linear function appropriate to that point . This graphics solution . y = 3x + 1
Answer b

We check choice by the system of equations , where substitute wartoćsi points Q and R to the model equations linear function


`\left \{ {{f(x)=ax + b} \atop {f(x)=ax + b}} \right. \\ \\ \left \{ {{1 =0 *a + b} \atop {7=2*a + b}} \right. \\ \\ \left \{ {{b = 1} \atop { 7 = 2a + 1}} \right. \\ \\ \left \{ {{b = 1} \atop {2a = 7-1}} \right. \\ \\ \left \{ {{b = 1} \atop {a=3}} \right.`

The result of equations confirmed our choice Answer b


Figure I'll add soon