no 23 tu caranya kyk mana ya? tolong bantuanya yaa

y = -2x + 9 ==> m1 = -2

ax - 4y = 5
-4y = -ax + 5
y = a/4 x - 5/4 ==> m2 = a/4

tegak lurus
m1×m2 = -1
-2 × a/4 = -1
-2a/4 = -1
a = -1 × 4/-2
a = - 1 × -2
a = 2

Garis y=-2x+9
Gradien = a/b=-2/1=-2

m1.m2=-1. ax-4y=5 -->-4y=-ax+5
-2.(a/b)=-1
-2.(-a/-4)=-1
2a=4
a=2