Page 37 - 新思维数学活动用书7 样章
P. 37

2   Expressions, formulae and equations



                      For each of these diagrams:

                      i   Write an equation involving the angles.
                      ii  Simplify your equation by collecting like terms.
                      iii  Solve your equation to find the value of x.
                      iv  Work out the sizes of the angles in the diagram.

                      v  Check that your answers are correct by substituting your answer
                          back into the original equation.
                      a                                   b                                  Tip
                                                                                             What do the

                          5x                                        6x   4x                  angles on a
                             4x                                                              straight line and
                      c                                   d                                  in a triangle add
                                                                             5x
                                                                                             up to?
                               3x  4x  2x                          3x              4x




                   11 Solve each of these equations and check your answers.

                      a  x + 12 = −6                      b  y − 9 = −4
                      c  3z + 6 = −30                     d  4w − 3 = −27
                   12 Zara solves these equations:
                        2a − 11 = −7     4 = b + 16                          I think that

                        6c + 7 = 25      −12 = 3d + 9                        a × b < c + d
                      Is Zara correct? Show all your working and
                      explain your answer.

                   13 Use the formula w = 2x + y − 3z to work out:
                      a  w when x = 8, y = −3 and z = 7
                      b  x when w = 15, y = 9 and z = −4

                      c  y when w = −10, x = 6 and z = 2
                      d  z when w = 20, x = 15 and y = 8






















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