IGCSE›Edexcel IGCSE Maths›Mind mapsLinear Graphs (y = mx + c)Edexcel IGCSE Maths: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsy = mx + cmmm is the gradientccc is the y-intercept, point (0,c)(0, c)(0,c)Positive mmm slopes up, negative slopes downRearrange so yyy is alone firstGradientm=y2−y1x2−x1m = \frac{y_2 - y_1}{x_2 - x_1}m=x2−x1y2−y1Rise over runKeep the subtraction order the same top and bottom(1,4)(1,4)(1,4) and (3,10)(3,10)(3,10) give m=3m = 3m=3Finding equationsFind mmm from the two pointsSubstitute one point to find cccOr use y−y1=m(x−x1)y - y_1 = m(x - x_1)y−y1=m(x−x1)(2,5)(2,5)(2,5) and (4,11)(4,11)(4,11) give y=3x−1y = 3x - 1y=3x−1Linear graphsy = mx + cmmmcccParallel, perpendicularParallel lines have equal gradientsPerpendicular: m1×m2=−1m_1 \times m_2 = -1m1×m2=−1Flip the fraction and change the signSpecial linesHorizontal: y=cy = cy=c, gradient 0Vertical: x=cx = cx=c, gradient undefinedExam tips2y=6x+42y = 6x + 42y=6x+4 has m=3m = \mathbf{3}m=3, not 6Check with the second pointDo both steps for a perpendicular gradient