Respuesta :

mathstudent55

Answer:

[tex]a \cdot b = 1[/tex]

Step-by-step explanation:

[tex] a = 5i + 7j [/tex]

[tex] b = -4i + 3j [/tex]

[tex] a = a_xi + a_yj [/tex]

[tex]b = b_xi + b_yj[/tex]

[tex] a \cdot b = a_xb_x + a_yb_y [/tex]

[tex] a \cdot b = (5)(-4) + (7)(3) [/tex]

[tex] a \cdot b = -20 + 21 [/tex]

[tex]a \cdot b = 1[/tex]

09pqr4sT

Answer:

[tex]\boxed{-20i^2 -13ij+21j^2}[/tex]

Step-by-step explanation:

[tex]\sf Plug \ in \ the \ values.[/tex]

[tex](5i+7j) \cdot (-4i+3j)[/tex]

[tex]\sf Expand \ brackets.[/tex]

[tex]5i(-4i+3j)+7j(-4i+3j)[/tex]

[tex]-20i^2 +15ij+-28ij +21j^2[/tex]

[tex]\sf Combine \ like \ terms.[/tex]

[tex]-20i^2 -13ij+21j^2[/tex]

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