Trong không gian với hệ trục tọa độ cho hai đường thẳng ; . Đường thẳng đi qua cắt lần lượt ở .Tính tỉ số .

Giải thích

. PT tham số của . . Khi đó: A B → = t - 1 ; - 1 - t ; 2 t + 1 " src="https://img-question-vn.ruangguru.com/7f0qefxTaWwsYZg7nJe8eiBC-91bJ3KyXjEC2p6cQ2JCk0F1EBGfk1Id4qLFPR21-usviQfgS3dCX_XVu3bks3iGr10jVnKceeiJOcRXJYpUWq7sHKz3f2vRVYsFXj-nZEWd24r8" style="width: 164.00px; height: 20.00px; margin-left: 0.00px; margin-top: 0.00px; transform: rotate(0.00rad) translateZ(0px); -webkit-transform: rotate(0.00rad) translateZ(0px);" title="stack A B with rightwards arrow on top equals open parentheses t minus 1 semicolon minus 1 minus t semicolon 2 t plus 1 close parentheses"> ; A C → = 2 s ; 4 s + 14 ; 2 s " src="https://img-question-vn.ruangguru.com/6qXU4UlYAuE2CpR_edOSFm6yqGSjrODBLQ76_MbgnlPFPrGANyWg5Y2EVj9L9EA_B44FU-RAsYFIuqJJ_zATgnZyzsKqVKHgzIrY4JQKInP_k7RwaEXdAkBnKc8UFMn0CJFpYFnO" style="width: 133.33px; height: 20.00px; margin-left: 0.00px; margin-top: 0.00px; transform: rotate(0.00rad) translateZ(0px); -webkit-transform: rotate(0.00rad) translateZ(0px);" title="stack A C with rightwards arrow on top equals open parentheses 2 s semicolon 4 s plus 14 semicolon 2 s close parentheses"> . thẳng hàng ⇔ A B   → , A C → " src="https://img-question-vn.ruangguru.com/Bkpm0f9ZDW-b_D0fgdlKiNOiIsaJaxPSdwGj2tVYYxyobDJIp4WLvPX216YoO8_pK22670R7oA-9mqWu0F4nIYzlTnGuHrjn2z4RhL0g5GossjoaV0LO9D1RSnFjbPSSkzFpl4MV" style="width: 69.33px; height: 21.33px; margin-left: 0.00px; margin-top: 0.00px; transform: rotate(0.00rad) translateZ(0px); -webkit-transform: rotate(0.00rad) translateZ(0px);" title="left right double arrow stack A B space with rightwards arrow on top comma stack A C with rightwards arrow on top"> cùng phương ⇔ ∃ k ∈ ℝ ,   k ≠ 0 ;   A B → = k A C → " src="https://img-question-vn.ruangguru.com/xNI8mJNTjNKclQtHQeLzcBvopFu8n-8tXvQH9Kk5RrFmQLsBAySXdsPjK41-x5dCNeeyYswOqb7RlUU8emska_1glgQeSMkTJxVJKb692RU5pQw0-fLuMVqKzTv4uM-4RWgblNMJ" style="width: 176.00px; height: 20.00px; margin-left: 0.00px; margin-top: 0.00px; transform: rotate(0.00rad) translateZ(0px); -webkit-transform: rotate(0.00rad) translateZ(0px);" title="left right double arrow there exists k element of straight real numbers comma space k not equal to 0 semicolon space stack A B with rightwards arrow on top equals k stack A C with rightwards arrow on top"> . Do đó: A B → = 1 2 A C → ⇒ A B A C = 1 2 " src="https://img-question-vn.ruangguru.com/ziJoki1DlKnVVTJJFEFIHIHWoMtz0cWRAcCUutdEjeFh5xAm9Go0waoOgI_TG01fgMapxRs3wqtNc1zpctsxLHrvu_3ja-w_Ta4TWqddg49GXxfMWYDlyTMy-T74AKVy9-14g3Ni" style="width: 152.00px; height: 34.67px; margin-left: 0.00px; margin-top: 0.00px; transform: rotate(0.00rad) translateZ(0px); -webkit-transform: rotate(0.00rad) translateZ(0px);" title="stack A B with rightwards arrow on top equals 1 half stack A C with rightwards arrow on top rightwards double arrow fraction numerator A B over denominator A C end fraction equals 1 half">