The teacher will be very surprised to see your correct solution 😉
sin(9*x) - sin(5*x) + sin(4*x) = 0
x1 = -31.7649923862968
x2 = 92.3628240155399
x3 = -11.9380520836412
x4 = -59.6902754216526
x5 = 7.85398163397448
x6 = -69.7433569096934
x7 = 4750.43715807817
x8 = 42.2369678982628
x9 = 70.162235930172
x10 = -5.93411945678072
x11 = -39.2699081698724
x12 = 50.2654824574367
x13 = -75.7472895365539
x14 = 71.5584993317675
x15 = 100.181899064475
x16 = 32.0442450666159
x17 = 35.8141562509236
x18 = 18.2212373908208
x19 = -77.8416846389471
x20 = -15.7079740344914
x21 = 54.1052068118242
x22 = -79.7964534011807
x23 = 21.9911516389414
x24 = -89.7099235525085
x25 = -14.451326206513
x26 = -47.8220215046446
x27 = -72.2566105174429
x28 = -25.7610597594363
x29 = -19.8967534727354
x30 = -86.0796387083603
x31 = 0.0
x32 = 48.3805268652828
x33 = 56.1996019142174
x34 = 43.9822971502571
x35 = -43.9822971502571
x36 = 1.88495559215388
x37 = 87.6155284501153
x38 = -55.9203492338983
x39 = 76.026542216873
x40 = -21.9911516375211
x41 = -83.2522053201295
x42 = -55.5014702134197
x43 = -95.9931088596881
x44 = -87.9645943005142
x45 = -91.8043186549017
x46 = 19.8967534727354
x47 = 26.1799387799149
x48 = -1.74532925199433
x49 = 98.0875039620813
x50 = 24.0855436775217
x51 = -98.6460093227195
x52 = -73.8274273593601
x53 = -63.8790506229925
x54 = 34.5575124991668
x55 = -52.010811709431
x56 = -17.8023583703422
x57 = -58.4336233567702
x58 = -24.5044226980004
x59 = 10.1229096615671
x60 = -29.845130209103
x61 = 86.2192650485199
x62 = 81.3323431429358
x63 = -68.0678408277789
x64 = 58.2939970166106
x65 = 62.2035345410779
x66 = 29.845130209103
x67 = -8.02851455917392
x68 = -99.9026463841554
x69 = 94.2477796076938
x70 = -82.0304748437335
x71 = -36.1283155162826
x72 = 84.1248699461267
x73 = -61.7846555205993
x74 = 95.9931088596881
x75 = -93.8987137572949
x76 = 4.53785605518526
x77 = 72.2566292962283
x78 = 80.1106126665397
x79 = 89.7099235525085
x80 = 59.6902749560156
x81 = 65.9734547403334
x82 = -65.9734546268699
x83 = 38.0481776934764
x84 = 68.0678408277789
x85 = 40.1425727958696
x86 = -33.85938748869
x87 = 28.2743275595482
x88 = -45.7276264022514
x89 = -7.33038285837618
x90 = -42.0973415581032
x91 = -3.83972435438753
x92 = 52.010811709431
x93 = 5.93411945678072
x94 = 14.3116998663535
x95 = -49.9164166070378
x96 = 45.867252742411
x97 = -28.2743358021627
x98 = 12.2173047639603
x98 = 12.2173047639603