The straight line given by y equals 2x plus 6 is drawn. At which x value does it cross the x-axis?
Ax = 3
Bx = 6
Cx = -6
Dx = -3
Answer & Solution
Correct answer: D. x = -3
1. Only two points are needed to plot a straight line graph, and the easiest two are the intercepts.
2. Every point on the horizontal axis has a y value of zero.
3. So set y equal to zero in the equation.
4. That gives zero equal to two x plus 6.
5. Subtract 6 from both sides to get minus 6 equal to two x.
6. Divide both sides by 2 to get x equal to minus 3.
7. The line therefore crosses the horizontal axis at the point where x is minus 3.
8. Answering positive 3 drops the minus sign, and answering minus 6 forgets to divide by the coefficient of x.
_Source: Siyavula Mathematics Grade 10 (Everything Maths, CC BY 4.0), Chapter 6: Functions_
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